[Closed] Told by Surveyor that our home insurance is invalid.

The mortgage company will almost certainly see it as an issue.

Mortgage survey already done, they are fine and the mortgage is approved and ready to go (and they also looked in the loft)

This is the buyers own survey.

Reporting him? Come on, he's not even working for the OP.

It doesn't matter who he's working for, if he's giving false information in survey reports (saying the house is uninsurable, when it clearly isn't) then his professional body, whoever that is, may be interested.

Edit- his employer almost certainly would be keen to know.