As Ricey says, could be a txt scam. Get a free pay as you go sim, put a fiver on it and contact them from that.
Also dubious about giving out address info without verbal contact first and preferably a land line.
I think it's because the calipers are so close to the rim that it is easy to chip them taking the wheels off. I have certainly noticed this with mine.
Maybe others will shed more light.
Quote from the add...
" in the U.S.A. where these cars are well respected & their owners spend vast amounts of money & time on them."
Is that implying they don't over here???
If you decide to buy it, PLEASE PLEASE get a FULL hpi check on it if nothing else. Have you seen the V5 doc registered in his name to his address? You know you can check all the old M.O.Ts online with either the V5 reference number or the number off the most recent M.O.T. This may also be useful when trying to track service history as it will give you an idea where the car was. .Also do an online check from letters on reg plate to see area it was originally registered.
Hope this helps a bit.