Should I serve a Notice or open informal discussions?
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 buy him or her out.
Exercising the right requires a formal legal notice to be served on the Freeholder and all* intermediate landlords. In claiming your statutory right the compensation to which a Freeholder is entitled will include any appurteunt property, possible retained land with development rights (a roof space) perhaps, loss of investment income, loss of commission from insurance premiums.
Serving Notice invokes statutory timescales for response. Errors in a notice may result in the freehold purchase being completed at the price stated by the party whose notice is not legally flawed.
Understanding what "premium" you should quote on your notice requires specialist valuation advice. 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.
Understanding what you should offer will require you to take specialist valuation advice. There are rather more factors in a collective enfranchisement valuation for say a block of 30 flats than perhaps 30 typical mortgage valuations. Primarily this is because the valuation methodology is set in statute and secondly because there is an element of assessing compensation due to the landlord and intermediate interests for dispossessing them of valuable title.