I think Photobox are excellent for prints - really fast delivery and good customer service. The quality and colour of the prints is really good. If you take a lot of pics its worth saving up until you have 500 prints (doesn't take long by the time you get copies for all the family!) as it works out really cheap per print.
I am less impressed with the photo books they offer. Have been disappointed with these - as they look like they are done on a colour laser. And have kind of felt I could have just made one myself.