I'm very sorry to hear this, Luckygirl.
The builder of the house I want has said he will give me "a couple of weeks" and the estate agent wants me to give my buyers time to sell again. But I have said I want my bungalow back on the market now and if the original buyers manage to sell quickly then they can still buy. I do not think agent is best pleased with me, but I need to take the right steps so that the builder knows I am seriously trying to move things forward.
I'd try to negotiate a bit longer with the builder of the house you're hoping to buy.
As far as the agent is concerned, you are the one paying him, not your buyers, and he should be working in your best interests.
He needs to put the bungalow back on the market immediately; you cannot afford to wait for them. That should spur them on, too. He's just being lazy.
You may find, in a buoyant market, that a cash buyer could come along.
Many years ago we had two potential buyers for a house, one couple tried to gazump the cash buyer but we chose the cash buyer as we needed to move in a hurry.
Good luck ?