I usually use Holiday Autos now. They are a UK firm who subcontract to local hire firms. I have never had trouble with them wherever I've hired cars abroad and I have no problem recommending them.
I used to use Europcar car but they have got very expensive and Holiday Autos are about half Europcar's rates. The reason for that is that HA have no fleet or depots to maintain. One example - Europcar quoted �280 last year to hire an 'A' Class car for 12 days in Mallorca. Yet Holiday Autos charged me �145 for a 'C' Class car for 14 days and that included Total Damage Waiver.