I had a friend to did this.
It was a while ago but...
The landlord was ok but it was the downstairs flat which was the nightmare. According to the lease details they owned half the loft (!) - I understand that's not uncommon as it's a common part of the building. My friend has assumed that they would want a token amount for the loft but actually they wanted a "proper" charge worked out on a square footage basis. I think they agreed 20k or so (it was a long time ago) but I'd get it checked out thoroughly by someone who knows how these things work!
I guess everyone is looking to make the most amount of money as is reasonable out of the situation!
Make sure you get a quote from your freeholder before buying the property.
Sloaney Pony wrote:The freeholders can make a lot of money
100% mark-ups on insurance
Very aggressive pricing of lease extensions
A lot of freeholds can be chased back to some very aggressive owners ... via companies in panama etc.