Karl Atkins

Hi all, Is there anyway to establish if building regulations have been followed/building control informed of work at a property. I'm looking to purchase a property that has its loft being used as a bedroom, I know the neighbours and they have suggested that it's a DIY job and the ceiling has not been adequately strengthened, I've asked the seller about it who deny this but can't produce any receipts or other documents to suggest otherwise yet it was only done in the past year or so. TIA for any advice.