of those my money would be on an M6 convertible - perfect as a weekend car, oodles of power, long distance comfort and touring capability, convertible for when the suns out and its got a V10 engine, way cooler than a V12.
To be honest if you aren't keen on the lightweight philosophy (lotus, VX220, Noble) then all the other cars listed will likely have high servicing and repair costs - but with a £25k budget, you could spend £15k on a minter of a TVR and still have a £10k fund for repairs.