I had 3 months left on my contract so called up Orange with the usual "I want to leave for a better deal" lines to try and get something good out of them. And here's what they offered, I thought it was pretty good and didn't need to think twice about accepting it.
Free HTC Desire HD
2000 Minutes (apparently existing customers get double mins)
500MB Data bundle
All for £20 a month on a 24 month contract.