Hi Coco,
I have (sped) read the hotels.com liability/T&C’s page. Basically they are waving any responsibility for anything that is third party. The only section they have to make a complaint is for you to write to them (email - reviews> - add at bottom of T&C’s page) if you feel a review of a hotel/accommodation that was listed on their site, that you then booked with them is not correct.
Sadly the co is based in Texas, so I don’t know how easy it would be to take up a complaint with the Hotels Ombudsman there.
There is a UK phone no (and I presume a UK office of the co), in which case, you could contact the Trading Standards dept and see what they say.
If your complaint is with the hotel here, then I think your best bet is to go through the Consumer Office/Reclamacion proceedure. (Don’t know how easy this is though if you are not based here.)
Good luck.