Following the withdrawal of Extra-statutory Concession 3.29, HMRC have published Revenue and Customs Brief 33/10 to clarify the application of VATA 1994, Sch 10 para 7.
In short, HMRC accept that, where the customer and supplier agree, the option to tax can be excluded on supplies of a building or part of a building that is to be used 95% or more for a relevant residential or relevant charitable purpose in specific situations.