In reply to colin struthers:
We used https://rentacarginer.es/en in November - no issues at all. Were met at Alicante Airport by a guy who more or less just handed us the keys (zero queue, took about 2 minutes) - no upselling of anything or extensive checking of documents etc. We booked the fully insured option. As many drivers as you like for no additional cost. No surprises at all in terms of costs.
Only thing to mention that was unusual was that we were instructed to pay in person at Giner's office in Benissa from Monday - Friday (we arrived on Sunday). It wasn't hugely out of the way for us, and again was quick and easy, but could be inconvenient depending on where you were staying.
Car itself was perfect, left it back in the airport carpark and posted the keys through a slightly opened window (as instructed), no issues whatsoever.