Buyer Creep

I had my house up initially for £260,000 and after a slow start we had a buyer (cash investors) come and offer £240,000. We said no and they upped it to £245,000. We accepted as we were hoping for a smooth transfer with no worries of our buyer having a mortgage denied.

We are now on week 13 and the chain is ready (3 houses) accept my buyer who has taken issue with the house being on an unadopted road.

They want me to reduce the price by £5,000 and pay £200 for an indemnity policy for the unadopted road. This is after we took £15,000 off the original asking price and agreed to pay £60 for the restricted covenant indemnity policy.

What would people do in this situation? I have been told that unless I accept they are prepared to walk away.

I know this is a tried an tested tactic by investors to up their profit margins, but should I overlook this and accept?

I know the decision is mine but just keen to know what other people think or have done in similar situations.

Thank you