How much is a freehold worth?

[toptop]

Thinking of Buying the ground floor flat and turning My flat and that one back into a house... The current owner of the flat up for sale has enquired to extend the lease (to enhance his chance of selling flat) with the freeholder, and �5k was the figure requested. If i were to buy the flat I wouldnt want the lease extended but would want the whole freehold.... How much should i expect to pay? and how did you come to an amount?

Many Thanks,
John

[Hawkwalk]

some good info here

http://england.shelter.org.uk/advice/advice-29 24.cfm#wipLive-8413-2