Oh, dear ...

I've just had a call from H at our Estate Agents. She overheard her colleague talking to our buyer, who was attempting to arrange a viewing of another property. Overhearing this, H asked her colleague to transfer the call.
"I didn't want to talk to you!" said our buyer.
"I know," said H. "But why are you arranging to view another property?"
"Well, there's no SOLD sign up so the vendor's showing no commitment." We're showing no commitment??
In brief, our buyers have done very little. They've arranged an appointment to discuss mortgages (which we had been told had been agreed in principle) for a week next Saturday. She's now talking August as a completion date, and denied that she had ever suggested mid-July.
H is going back to her to say we will put a SOLD sign up, but if no survey has been done within 2 weeks of their meeting the mortgage people, we will put the property back on the market.
I am physically shaking as I write this. It seems it is certainly too soon to be thinking about finding a place to let. These people, if they don't drop out of the process, will probably at least drag their feet. We may be in for a rocky ride. And I've been sweating over how to ensure we don't keep them waiting for completion, and even planning to prepare a nice little handover pack of instructions etc. for them. Why are there not more nice people in the world??