Have just installed a Chinese bottom rad, the thread for the thermoswitch is too small for the switch, don't really want the Hassle of sending it back, so what are my options (if any), could I possibly run a tap through the thread or would that be a no no? Could I get hold a smaller switch? Any other opinions?

How much smaller is it? Can you measure the switch and the thread in the rad? If there's enough metal on the boss I can't see why you can't drill it out and tap it, just put the hose pipe through it before fitting.

+1 on drilling and tapping it.

Kennon

Yeah tapped it out today, cheers for your input!