Lambeth Council are difficult to deal with, we have a flat bought right to buy 32 years ago so we are considering a lease extension as we've 93 years on ours. There is a need to extend before it gets down to 80 years as the extension cost calculation changes to include "mariage value" for the Lessor. Also you will need to own for two years before you can extend, unless you can get the seller to extend as part of the sale and Lease assignment process, but that may be a step too far with Lambeth Council involved.
Elam Close is part of an estate and you will pay service charges to the Council for works to the estate cleaning, gardening, maintenance, as well as work to the structure of your own building, external decorating, window renewals and roof repairs. The Council do Major Works in fits and starts and get robbed blind by their contractors then pass the cost on to you.
In my involvement with Tenants and Residents, Area Forums, Leasehold Council, Major Works reviews and now the Leaseholder Association we have fought continually for better service, value for money and proper oversight for years.
We do have some victories and I am probably known to many Council Officers as a serial complainer but my work gives me some advantages and we have a good group of people on our estate. Don't take on a Local Authority Leasehold unless you are prepared to spend a significant amount of time dealing with unreasonable systems run by people who are unable to see the damage they do.