I use hotels.com a great deal, probably 50 nights this year at least.

If I'm flying return with BA, I also look to see what 'holiday' options they have, even for business trips. Often a big discount over flight + hotel with either hotels.com or going direct. More likely to include breakfast too for some reason.

A few % on topcashback is available on either method, and BA chuck in a few Avios extra for your hotel booking ... so there's not a whole heap in it, just go with the cheapest deal for the nicest hotel.

I've never worked out the booking flexibility with 'holiday' bookings on BA though...