For questions about leasehold law in general, an excellent starting point is a site curated by Mark Chick, a practicing leasehold lawyer. The links below go to www.leaseholdinfo.com.
Will the ground rent increase after a lease extension?
I am a freeholder. Do I have to grant a lease extension to the leaseholder?
What happens if we cannot agree on how much the lease extention should cost?
I want to extend my lease. Are there any additional costs payable other than the price of the lease extension?
Do I have to go through the Act to extend my lease?
How long do I have to wait to extend my lease?
Am I a qualifying tenant for lease extension?
How long do I have to wait to extend my lease?
What happens when my lease runs out
Who is responsible for maintaining the structure of the building?