Thanks all for your replies and suggestions.
I've been to see the mortgage guy at the bank and handing the keys back is going to be a no, renting it is a hmmm maybe, and keeping it on the market and trying to maintain a positive outlook is going to be hard!
Apparently because we're still trying to sell we can't change the mortgage the way we would if we just decided to rent - which is good because we have a really good rate (repayments of just £250 a month) and as we are renting to our son we shouldn't have to. But the housing benefit people won't like that so son may be living rent free until he gets himself a job. Which does actually save us money in the long run as he was eating his way through about £50 a week living here!
The selling it part is hard, not just because the market is rubbish at the moment, but because of the added issue of the lease and there being a third party involved in the shape of a property management company acting on behalf of RBS who own the freehold.
It wasn't a problem with the last company as they got work done and returned my calls, but GVA -who are in charge now - are giving me the run around.
We did try selling at auction, and got an offer of £52k, but with the astronomical fees we just couldn't afford to sell. Obviously we owe less now, and have a bit more money in the bank to cover the shortfall so we may be able to go back down that road.
I considered the "we buy any house" brigade but they all seem so dodgy that I've been put off.
If I'm honest I just don't want to have to think about it till after xmas, but son rang earlier to say the roof is leaking now so I'm going to have to do something pretty quickly or there won't be anything left to sell!
Anyway, thanks for listening, I'll keep you informed.