Is there a generally accepted formula for calculating the freehold?
Yes there is a formula – but in the end, I think it comes down to negotiation. There’s an arbitration service. You would have to prove the landlord’s being unreasonable, and then shell out to get the arbitrators on his back, but you can claim some of that back if you win, and I’ve heard they’re pretty sympathetic to the leaseholder. I know this becuase I’ve got a dodgy landlord who tried to charge us a fortune. My recommendation is to keep records of everything and use the Leasehold Advisory Service for free advice.