David, I am not aware that HMRC have accepted that this works. However there is a clue that this works from para 18(5) of Sch 4ZA which says that the substantial performance of a contract for a building that is to be constructed or adapted for use as a dwelling and construction or adaption has not begun at the time of substantial performance is to be treated as the acquisition of a dwelling. By implication this provision would have been unnecessary if the sale of bare land that was going to be used for the benefit of a dwelling was already caught (see also para 18(4)). You may be ok therefore but I suggest that you do not substantially perform the contract and instead complete on it as bare land with the old building completely removed and work on the new ones yet to commence.