The right under the Leasehold Reform, Housing and Urban Development Act 1993 is to add 90 years to what is left on your existing lease.
Browsing: Extending Your Lease
The valuation formulae are complex but are primarily based on compensation for loss of ground rent and the length of the unexpired term.
The Law Society of England and Wales is advising leasehold property owners to take advantage of lower property values and extend their leases.
One way of obtaining a long lease is to collaborate with other owners in the building to exercise the right to collective enfranchisement.
Selling with a short lease can be overcome and this can increase the value and the marketability of a flat.