A difficult question!
Some Freeholders will quite rightly refuse to entertain discussions without a formal notice. From the Freeholders perspective, without formal notice he/she is at risk for fees to cover professional advice they need to negotiate with you.
That being said, if your freeholder lives in the block it would be better to have a chat first. Strangely some freeholders still need educating that it is a leaseholders right to claim a statutory lease extension.
The Notice that you have to serve on the Freeholder and all intermediate landlords invokes statutory timescales for response. Errors in a notice may result in the lease extension being completed at the price stated by the party whose notice is not legally flawed.
The information a Lessee need to state on their notice includes:
Understanding what "premium" you should quote on your notice requires specialist valuation advice. There are rather more factors in a lease extension valuation than perhaps a typical mortgage valuation as set out above, also there is the element of assessing compensation due to the landlord and intermediate interests for postponing their valuable reversion by a further 90 years. The leaseholder claiming his/her rights is the party that in law is responsible for both parties costs and it is our understanding that if the residents have served Notice then the Landlord's surveyors fees form part of the purchase price together with reasonable legal fees.