Lease extension

Other

My flat has an original 99 year lease that is now reduced to 81 years. The Management company are quoting me £1000 plus VAT on behalf of the Freeholder to cover legal and surveyor fees simply to claculate the sum it would then cost me to increase the lease back up to 99 years. This seems astronomical to me as other similar flats in the block must have already been assessed for this lease extension. Is there any way of avoiding this charge or do I have to pay it to receive my quote? I understand that if the lease falls below 80 years there may also be a supplementary charge called Marriage tax? Is there any way of assessing how much this would additionally add if the lease was not extended within this timeframe?
Thank you.