In reply to RR:
Thanks.
In the end I made a ring out of a bit of steel roofing strapping from Wickes. The stuff that's about 25mm wide by about 1mm think with loads of holes in it - works fine with trangia pots.
Also, by coincidence I was climbing in Scotland this week and popped into Ellis Brighams in Fort William and they had the MSR Alpine 2 pots. They are much bigger than the photos on the Internet suggest so I think if I want to use pans to cook stuff in I'll make do with the home made ring and the small pans/lids from my old olympus stove.