Is that correct? My understanding is that caterpillar tracks and asphalt roads don't mix.Besides, modern trunk roads are good for testing tanks as well.
AIUI the underlying problem with British tanks designed after 1934 IOTL was that the prototypes weren't tested properly before being ordered into production. However, this wasn't due to incompetence or inadequate facilities, it was due to insufficient time.
ITTL there won't be enough money to replace the A2 Medium tanks with the A6 or A7 between 1929 and 1934. However, there will be more R&D money for AFVs including tanks over this period. As a result the specifications A8 to A12 will be issued a few years earlier. This would have given the Army time to test them properly, sort out the mechanical faults and only order the best designs into production.
AIUI the Army bought so many Mk VI light tanks because nothing better was ready and they couldn't spend all the money the Treasury had given it to buy tanks. ITTL something better would be available because they had been in existence for some years and had been properly tested. Therefore, they could put the best cruiser tanks (which AIUI was the A10) and the best infantry tank (which IAUI was A12) into production in 1936. As already related these tanks would have had their mechanical problems sorted out before they were put into production.