In regards to the 1080p vs 720p question, you will notice a difference when watching a blu ray, but for general tv viewing, it could be argued that 720p gives you an as good, if not better picture.
If you are happy with your tv, and there's nothing on the market that is screaming "buy me", I'd stick with what you've got until either the tv dies, or a better alternative presents itself.
Oh, and don't buy from Currys if you do decide you want one, Richer Sounds offer a free 5 year warranty with all their tvs now, as do JL.