We've used Dickmans before and they were fine.
Although when we booked it said that there would be a transfer to pick the car up, the car was actually waiting for usin the car park of Murcia airport. If you leave arrivals and cross the road into the car park you will see lots of smaller car hire companies based there, all working out of vans where you can end up doing the paperwork by torch light. That said the rental was good, as was the price.