Well postscript to above. Met with UB, the adviser was lovely and really knew her stuff. While I don't have negative equity and would have a lot of savings, I got scuppered by the salary multiples - 3.5 times my (very average) salary wouldn't get me enough to buy a house.
She did mention a 10 year Home Mover mortgage, but only certain branches are authorised to grant this. From what I gather I am eligible. I would be fixed for 10 years on a higher tracker of 2%+ECB for the balance of my current mortgage and a pay new rate on the extra borrowed. It looks like my only option if I want to move.
Anyone hear of any downside to these (apart from losing my tracker, which will happen regardless if I move).