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I had already e-mailed to the hotel with no response, so i took advice and phoned the hotel. It took a while to find out, but in fact, there was no reservation for us, so I was right to worry.
They did tell me that they were changing the way they booked rooms, and in fact their website is now very good, whereas it was very difficult to use before, would not load and couldn't get it in english (the hotel website not booking.com!) They are not using booking.com now, and it seems that booking.com took my reservation, and confirmed it but had not sent it through to the hotel. We arrive late in Granada, and wouldn't have wanted to try and find somewhere else to stay, if booking.com had failed us.
In the end, the hotel is available on other sites such as expedia, hotels.com etc. Have used expedia before and have been very pleased with the way they dealt with problems. I feel that I don't want to use booking.com now, even though all the hotels we have booked with them before have turned out OK.