Loft space prices for leasehold properties

[BeePolite]

I am the leaseholder of a 1 bedroom first floor flat but the loft space was not part of the demise, I have now been given the opportunity to purchase the loft space from the council with future plans to build a loft conversion.

My question is has anyone been through this process and what sort of prices where they given for the price of the loft space. I have scoured the internet with a lot of various and confusing advice, in your replies you do not have to give personal details but a rough idea would be appreciated. I have posted the same message in the residential part of the forum.