In a similar position… I understand what is required is:-
A Jan 1999 capital valuation is required to calculate the social rent applicable to the completed units. It should be a red book valuation of the sale value of the dwellings (or a sample one) assuming the remodelling was completed at that time and with vacant possession.
For valuation of a ground floor and first floor flats I’ve been quoted £1650 + VAT
Sounds a lot so I’m too trying to find an alternative.