Thanks for the information everyone. My solicitor put me in touch with a company who specialise in doing lease extensions for groups. I was unable to find out there estimate for extension but will ask again. They had a meeting of interested Lease holders about a month ago. I couldn't go as I am still abroad.

Alas I have to wait 2 years after purchase as I bought a repossession. Yes I know - but it is the tiniest studio I have seen, and all I could afford.
If anyone is interested in the website for the firm I can send it.

To the those who spoke about high service charges and extras. Yes, the service charges are high AND they do hit you with large bills for major works not covered. I have to tell myself it is an attractive building, iin a good position.