I had a 50" plasma and I would say, if you want to go bigger than your 55" tv, it's got to be a projector. Much more bang for your buck. Also, if you sit 10 feet away from a 65" tv, the picture will look terrible. You don't have that issue with projectors. I sit 9 feet away from my 106" screen and it looks stonkingly good. A proper cinema experience.
£1500 would get you everything: an Optoma HD33 projector, screen, mount and all cables.
Just food for thought.