Many on this here forum will be familier with the efforts of the British Goverment from 1935 to leverage existing Aircraft industry as well as the then British automobile industry to put into place
Shadow Factories that could in time of war allow Britain to rapidly ramp up aircraft production.
This plan of course would eventually extend to Canada, South Africa, Australia and New Zealand
What if they had done the same thing with AFV production pre-war - that is setup additional factories and /or leverage locamotive/boiler makers to allow for an increase in the heavy industry required to produce more AFVs.
On the outbreak of war Britain had made just 2 Matilda IIs and during the battle of France it had only delivered 2 dozen or so with only about 140 odd Crusier tanks and relied heavily on the MKVI light tank and Matilda 1 infantry tank both of which were machine gun armed AFVs.
Now the British Army had known for a time that those 2 light tanks would be ineffective in battle and had sought to replace them.
Now had a AFV Shadow Scheme been stood up how much better would British AFV production have been by 1940?
And too acheive it what industries could have been leverged and specifically what was lacking OTL that could be addressed with this scheme?
As for the money for this - well Looking at the data that NOMISYRRUC provided
here on British Spending leading upto WW2 - have the HMG allocate increased funding earlier in a more controlled fashion rather than waiting till the '11th hour' and panicking