Clarkie, you could try these ones.
Two of them are closer to Bath, one's in Melksham, and Avis Prestige you can probably /possibly get from Bristol Airport or the central Avis place in Bristol.
http://www.vintage-classics.co.uk/
http://www.greatescapecars.co.uk/locations-bathfleet.asp
http://www.avisprestige.com/
Some lovely cars, nice E Type Jag on the Great Escapes site, not too expense