Long term lease - extension permit charge

Mike here,
We have a semi detached house with a 950 odd year lease and pay £6.50 a year…
The deed seems fairly basic.
We want to get an extension and they have said they will only sign the consent document subject to their costs of £1200!

  1. Is there any rules / formulas for such a fee.
  2. We asked to buy the freehold but they wanted £20,000 for it!
    We bought the house for £425K in 2016.
    Any advice on whether this is fair?

Hi Mike I only have a vague recollection but my sister does convyencing and I seem to remember her speaking about a fair scale of charges. Consult a property lawyer