I have relatives selling a rural one-off who have still not signed contracts on a house that went sale agreed six months ago.
Buyer's lender raised issue about boundaries that needed an architect's report, then a planning issue related to a misplaced septic tank from the 1980s. They need confirmation from CC that enforcement action was never taken.
All of these issues were present when relatives bought in 1990s but lenders seemed less bothered then. Am not sure if criteria are stricter now but it's worth bearing in mind.
@MandyD - it's not impossible that your own lender might raise the boundary issue before drawdown.