18 BB's in 10 years is easiuly inside the armour availability.
In 1938 the building plan was 2 1/2 BB a year, and with an increase in the armour capability could have been raised to 3/year.
After that, other issues such as guns and FC equipment get to be the bottlenecks
But starting in 35 and ending in 45 1.8BB a year is no trouble, and they would be able to build the armourced carriers and cruisers as well.
However I think they would also replace all the early, experimental carriers by then, they will be getting too old and worn out - although its possible they may keep Courageous/Glorious as a training carrier, although the plans did include one as well as the other carriers.
Depending on what other contries are doing they may build extra, probably larger, fleet carriers, and quite possibly more Lion types that BC's, allowing the QE class to be in reserve.
The armor question is to be seen against other requirements as well, sicne armored vehicles too need it, as do aircraft in a lesser amount (Pilot seat armor in the Spitfire and Hurricane) The industrial output in the UK for the high quality facehardened cemented armor was facing a shortage in the late 30's as the buildign of both battleships and aircraft carriers was in full production by then, so a vast quantity of a slightly lesser Chechoslowakian Cemented Armor was purchased to cope with the shortage. This armor was mainly put into HMS Formidable and Indomitable as flightdeck armor, while the more superior British cemented armor was put into the King George V class battleships.