So there's good news our end - we've exchanged! Completion is set for next Friday the 20th, I've booked the removal company. Very excited. It was painfully slow at the end - our buyers signed contract didn't arrive with their solicitor (no idea what that means - lost in post? We've done ours online), held the whole chain up. It also seems that if everyone doesn't exchange by 5pm, some deadline is missed and everything has to happen all over again the next day.
@goldvelvet sounds like you've done exactly the right thing being honest with your buyers. I think worst case they pull out and you remarket, doesn't sound like you'll lose your vendor. Are your buyers in a chain? If not you've got a better chance of them waiting.
@ojbsmum we're moving from flat to house - I can't wait to have my own stairs! And back door! And garden! (you get the picture)