Soooooooooo.........
A inherited a house and garden in 2004. He has a base valuation for both in 2004.
He sells the garden. He may or may not have had a CGT liability/ paid CGT - nothing to do with the purchaser.
His base valuation for the house remains as at the apportioned 2004 valuation - it, the house, would not have been re-valued. By anyone. He was not selling the house so he had no gain.
A is now selling the house. It is possible that he had a high base valuation in 2004 - near enough to the height of the boom- and that the current market value is in or around what the property was valued at in 2004.
It may also be that there was a low base valuation attributed in 2004 - especially if A had a potential CAT liability on the inheritance.
This is quite common - people sometimes think that a low value for Probate is a good thing. Except it may not be when it comes to a sale, down the line. And the sale price is way higher than the Probate valuation so now they have a CGT liability.
The house now has a value- its whatever something similar would sell for in the locality - now, we'll be told there is nothing similar!
Call it 200K- or any other figure plucked from the sky? Is that a realistic market value? Or so low that it will trigger a Revenue enquiry?
Revenue have an astonishing breadth of knowledge of valuations for CAT, CGT and stamp duty so any variations are likely to trigger Revenue interest.
For the OP - if you want to buy the house, make an offer of what you think it's worth. If the vendor wants more or less, that's up to them.
mf