On the off chance that anyone has had a similar experience/has advice. I share a roof terrace with neighbours who rent their flat out. I have direct access to the roof terrace, their tenants have to exit their flat and climb stairs to do it (and don't really use it). If possible I'd like to buy their share but don't know how much to offer (it's a mediumly nice bit of London) - £20,000 perhaps? We all own a share of freehold and there have been no problems between us as freeholders - relations are good. We all have responsibility for external works on the building.