Expedia.co.uk

Fantastic!

When I had a problem with a hotel and the hotel refused to even acknowledge that I was trying to give them a complaint upon check out (I was there for one night only) just said "oh ok bye", I went to Expedia and they were so helpful.

As well as that though I like the "welcome back from" emails.

Not so much the "continue booking your trip to....." when all you were doing is browsing.... or when they can clearly see that you are flying somewhere for one day then flying somewhere else from there, they still think you are spending all your time in that first location.....

However, sometimes it's useful and sometimes there are good deals sent to you.

All in all I will use Expedia where I can, unless (a) the airline does not use them for example Singapore Airlines and (b) it's exceptionally cheaper elsewhere.