A few general points, give that some people seem grossly ignorant about the state of Britain in 1919.
OTL even after victory Britain came close to revolution in 1919. Troops, armoured cars, artillery, tanks and warships were widely deployed to maintain order. The view that the British military was monolithically loyal to the government is a superficial one that doesn't stand up to scrutiny. There were numerous (illegal) military strikes and outright mutinies in 1918-19. Some examples:
1. In Purbright camp in early 1919 machine-gunners of the Guards went on strike
2. On 13NOV1918 Shoreham camp experienced a full-scale mutiny over conditions and the slow pace of demobilisation. The troops won and were released from service rapidly, by the thousand.
3. On 09DEC1918 Royal Artillery units in Le Havre rioted and burned down army depots.
4. January 1919 saw sustained and violent mutiny and rioting at the camps around Calais, including the election of a Soldiers’ Council at Valdelièvre (where the rebellious troops fortified the camp against attack. The military headquarters at Calais was occupied and a Soldiers’ and Sailors’ Association twenty thousand strong formed. The mutineers enjoyed extensive support of French civilians, including railway workers who refused to transport troops to suppress the nascent Calais Soviet. When Byng finally arrived to suppress the mutiny he found his troops unwilling to fire on their own.
5. A mutiny at Felixstowe saw over ten thousand men voted to form a Soldiers’ Union and refuse to obey orders until their demands were met.
6. At Kimmel Park camp over 15,000 Canadians rioted in early March 1919.
7. The period January-March 1919 saw a huge number of muties and "acts of disobedience to lawful authority" at Aldershot, Biggin Hill, Blackpool, Briston, Chatham, Dover, Fairlop, Folkestone, Grove Park, Kempton Park, Maidstone, Osterley Park, Park Royal, Shoreham, Shortlands, Southampton, Southwick, Westerham Hill and elsewhere.
8. In addition there were outbreaks of disobedience at several railway stations (mainly in London) where troops refused to embark for France and (especially) Russia.
9. The Royal Navy there were refusals to weigh anchor for Russia on numerous occasions in 1918-19 at Invergordon, Portsmouth, Rosyth, Devonport and Fort Edgar.
10. In February civilian workers at Rosyth discovered that the cruiser they were involved in refitting was to go to Russia; with members of the Socialist Labour Party they leafleted the crew, who refused to sail and were paid off after a three-week standoff in the port. This civilian resistance to intervention in Russia, suggests an active Labour/Union force available; for example in May 1920 dockers in the Port of London refused to Jolly George with an arms consignment for Poland.
11. Rosyth saw other mutinies, for example that on the mine-sweeper detachment in January 1919.
12. A few days later the patrol boat 'Kilbride' at Milford Haven mutinied and raised the Red Flag.
13. At Port Edgar a destroyed flotilla due to return to Russia was a hotbed of rebellion; eventually less than half the ships departed, with crews drawn from Atlantic fleet battleships. Some of the destroyers' crews evaded the security at the port and (with assistance from others) 44 men made their way to London to present petitions at Whitehall.
14. A Royal Marine battalion at Murmansk also mutined, with two companies refusing orders.
1919 saw active resistance to the British government in Scotland, parts of Wales, Ireland as well as cities like Liverpool.
1. Warships (including the battleship Valiant) were sent to Liverpool in a show of force, with orders to occupy the docks and be prepared to bombard the city.
2. Thousands of troops, with tanks and armoured cars in support, had been deployed "suppress disorder" in the streets of several cities. Including Liverpool
3. The "Battle of George Square" on 31JAN1919 occurred when Glasgow police attempted to suppress strikers. Churchill ordered soldiers and tanks to the city to prevent any further gatherings and to deter a "Bolshevik uprising. There were explicit parallels with the 'Forty Hours'. Scottish units were confined to barracks/camps under guard due to fear of mutiny and insurrection.
4. Over a thousand soldiers had marched under arms on Downing Street in early 1919, before being disarmed by a battalion of the Grenadier Guards loyal to the government.
5. Rioting in Luton had led to the arson of the town hall and further deployment to troops.
Let's examine some happenings in the pre-war period. Well before the war began there was plenty of industrial unrest in Wales and elsewhere; it's known to historians as the "Great Unrest" of 1910-14. In fact there are some (not me, I consider late 1918 to 1919 as more likely) who consider one of the most probably occasions for revolution in Britain was 1910-11, especially during the National Rail Strike in 1911. The strike was brief (only two days of full scale disruption) but showed to the Liberal government the power of the new union movement.
Asquith and Churchill (who was still Home Secretary, having not been relegated to the Admiralty for his idiocy at Sidney Street yet) promised the extensive deployment of police and troops to keep trains running; thousands of troops were deployed, many against the wishes of local authorities who felt their present unnecessary and provocative (Churchill has, with Aquith's approval, suspended the regulation requiring local authorities to request military aid).
One of the results of this was the "Llanelli riots" which saw pitched battles between strikers and their families and supporters, and police and troops. Six people were killed (two when troops illegally fired into a crowd and four in an explosion on a munitions train moving supplied to Ireland) and the locals responded by 'burning out' magistrates, police stations and local businesses. More than one hundred people were injured and at least one soldier refused orders to fire on civilians. He was arrested but escaped from custody (it's believed with assistance) which sparked a mutiny panic.
In 1911 there was the Liverpool general transport strike, in which an alliance alof dockers, rail workers and sailors, paralysed commercial activity in Liverpool for nearly three months. The authorities responded violently; on 13AUG1911 a mass meeting on St. George's Plateau, was baton charged by police, leaving around five hundred people injured. On 15AUG a relatively peaceful crowd was fired on (again contrary to common law) by troops of the 18th Hussars; two men were killed (both shot twice) and fifteen were injured.
Churchill responded in much the same way as in 1919: by deploying additional troops (on top of the ~four thousand already in the city) and sending two cruisers (Antrim and Warrior) with contingency orders to bombard the city "if necessary"
By August, when the strike was settled, food was in short supply in the city as goods couldn't move without a Strike Committee permit but the authorities threatened to arrest those who obtained them. Interestingly the strike managed to unite the generally antagonistic Green and Orange factions, with bands marching together.
1912 saw Britain's first truly national coal strike. This was settled by the government, after five weeks, who basically gave the strikers most of their demands. The strike hugely disrupted travel and transport, and effected military and naval activities. There was relatively little violence (though some staff who attempted to evict miners' families from homes owned by collieries, on which rent wasn't being paid, were warned off). The dispute did see the first moves towards a volunteer "Civil Guard" with a civilian volunteer force being formed to supplement police, 'specials' and troops.
It's important to remember that Britain (like Russia, France and Germany) was undergoing huge social and political change in the period. For example:
a. On 10JAN1911 at the Central Criminal Court suffragist Emily Davison (she of the "resident in the Palace of Westminster" stunt) was jailed for six months attempting to destroy the contents of Post Office letterboxes.
b. There were outbreaks of suffragist vandalism in March, with hundreds of windows smashed.
c. 31MAR saw a demonstration in favour of Home Rule in Dublin, with over a hundred thousand people present.
d. 09APR saw a demonstration against Irish Home Rule in Belfast.
e. March and April saw around twelve thousand Singer workers strike on Clydebank in support of dismissed women
f. On 21NOV suffragists stormed the parliament buildings.
g. On 18AUG the House of Lords is neutered by the 1911 Parliament Act, much to the horror of peers and Unionists. The act specifically allows for the upper chamber to be replaced by an elected assembly.
h. The London labour movement established it's own newspaper (which became the Daily Herald in 1912) to promulgate a pro-labour, pro-union and rather revolutionary message. Lloyd George did not approve...
The "establishment" was scared. The hysterical reaction to Mann's "Don't Shoot" leaflet of 1912 (suggesting troops refuse to fire on civilians) was one example of this.
The idea that Britain was a monolithic bulwark against socialism and communism and completely stable before and after the Great War is utter nonsense. Despite being so dearly held by certain people.