My local Tesco is pretty limited for soy or mushroom based vegetarian food, anywhere I can get hold of these things?

Have you tried:

TOPS

Rimping

Makro

Big C

Makro has textured soy protein, the dried kind--at least the Mae Rim branch has it. There's a vegan restaurant and temple on the ring road that passes Ruamchoke, it's West of the Rimping intersection about 100m. Can't miss it it's got a big statue of Guan Ying in the back. They sell supplies there too in the restaurant.

okydoke will try thanks chicog/seesip