Hi,
Thanks for the comments / responses.
Monkeyboy - your comment re his 'opening gambit' was right on the button. I've told tenant that 17 times rent is too low and he is gone off to do his sums again.
At the moment, I'm not inclined to let it go at anything less than full market value (definitely no reduction for rent paid!). I don't mind whether I sell it or not and if the tenant really wants it then there is a good argument to say that he should pay a small premium over market value to do so. The big question is - what is market value and I'll only find that out if I put it on the open market!