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