In reply to mike123:
I highly recommend
http://www.malagacar.com/ , I’ve used them 6/7 times and always been happy. Plus they are much cheaper than most places and have full insurance with no excess (check out the details I think it excluded underbody and some other things).
They have two options on fuel, ½ full to empty (but at a reasonable fuel cost i.e. £30ish), or they charge an extra 20 Euros for ½ full to ½ full.
I paid £230 for a 1 series BMW for 2 weeks, including the half tank of fuel. Could have been £90 if I’d gone for tiny car.