It's usually thought best not to disrupt children more than necessary when their family breaks down and for them to remain in the FHM if at all possible. So the first consideration is your wife's ability to raise the mortgage and if she can't then realistically the property needs to be sold. mediation or even collaborative law are certainly better ways to proceed than slogging it out through the courts.
One thing you need to watch is that three years after you moved out of the FMH the principal private residency relief from capital gains tax ends. If you haven't bought another property you can still nominate the FMH for relief but you need to talk to HMRC. There is a download about CGT available from the finance bit in the Divorce Forms and Information section, accessed through the Resources menu at the top of the page.
Sorry Fiona, but I think 3 years down the line, a move of house would not be a problem. Many people move house more than once in their childhood whether as part of a 2 parent family or just with one parent. As long as the move is handled properly can't see a problem. And if Rob staggers his move, then their daughter will still have some security whilst adapting to her mum's new home. As long as they ensure their daughter can stay at the same school (if she has already started school) then I think she will have enough familiarity to cope well with the situation (after all they have been apart for most of her little life).
Sorry, I didn't make that very clear. That wasn't a personal view of mine about moving. Our teenagers were looking forward to the prospect of moving and were disappointed when it didn't come off!
However, the Courts will not usually expect someone to move and risk upsetting the children further, especially if it involves changing school and loosing friends unless there is good reason eg the FMH is much bigger than requirements dictate or some equity needs to be released to home the NRP.
thanks very much to both of you - you've helped put may mind at ease that I'm thinking in the right direction. Any move from FMH would be within the same area and would mean that my daughter would not change schools, disruption would be minimal - thats my plan anyway!