In reply to Pete Wimbush:
Have used centauro at Alicante for a couple of years in a row now and they were OK. Used to alway suse europcar who were mostly excellent (except one year where they were spectacularly bad in a very expensive way ... but, even then, did get my money back after complaining).
I think the price is very variable depending on when you go. I usually go over christmas and new year and it's expensive. I'd say 300euros for 10 days is pretty standard if you're going at a busy/popular time (and don't want to risk the likes of goldcar).