FTB here. Just found out from the solicitors that there are no building regs on an attic conversion. It was advertised as a 2 bed, which included the loft, and seems priced as a 2 bed when compared to similar old terraces in the area. Its also registered on Zoopla, everywhere as a two bed ect.
The loft conversion was there in place when the seller brought - the previous owner got indemnity insurance or something. My offer was a couple grand more than the seller paid more than ten years ago(during the boom I think.)
Its a teeny tiny terrace with 1 reception at the bottom of the market. The attic room would need to be in constant use.
There's not a lot going in the area, and this house was in the perfect location - not sure what to do!