A search done with the Coal Authority is supposed to reveal whether any past, present or future activity in the area has or might cause damage to a property.(posted 8647 days ago)The Halifax will have made their decision as to whether or not to grant a mortgage based on the survey's that the Coal Authority have given your buyers.
Your wife should ask the buyer's solicitors for a copy of the mining search (or ask her solicitor to do it for her).
Your wife should also go back to the solicitors who acted for her when she bought the house and take a look at the mining report that was done then.
Once you have copies of both searches, you can compare and see if there have been any significant changes since the last survey was done.
If there are no significant changes since the last survey, then your wife's solicitor can go back to Halifax and question their decision. If not, then you'll need to investigate further.
But do get copies of these mining searches, even if your sale does fall through. And please don't consider handing in the keys until this has been sorted out.