Thanks Richard,
Mike Barnby sounds good and clearly he knows a lot about magnesium alloys, as can be seen from his website:
http://www.mb-racingwheels.com/index.htm .
The big Brands event this year is 30 June/1 July - when I hope to be sunning myself in Greece (!!), so sorry to say I will miss it.
I am still hoping to find some allow wheel skills a bit nearer me in north London. Meanwhile, I am happy to continue to use my car with one wheel having a very slow puncture. It loses about 4 lb/squinch over a three week period and I suspect this is because the aluminium/magnesium alloy has become slightly porous. Has anyone else experienced this?
Colin