At the club I used to go to, which was in Chingford, there was no stock class. It was just completely unrestricted. Had there been some attempt at a stock class, it may have kept my interest.
I think the only car that Tamiya developed that really was competitive, albeit for a short time, was the Brat/Frog chassis. With dampers fitted on the front suspension and a decent motor, they gave the Scorpions and Hirobos a good run for their money.
I always had the most cars in the Tamiya line. Had a Sand Rover, which I loved, but basically wore out with use, and spares availability back then wasn't always great (pre-internet). This was replaced with a Grasshopper, which was an improvement with an enclosed gearbox and differential, but handling wasn't the cars strong point, and I always missed the beach buggy looks of the Rover. Both cars were upgraded with a 540 motor.