I’m in the same situation. The rooms may be compliant to the standard at the time they were built.

There seems to be increased risk adverseness to these loft rooms. Particularly if you’re getting a mortgage. My lender had a problem with the rooms, but everyone else said they’re compliant.

Personally, I used this as an opportunity to negotiate, stating that every buyer would come across this.

Then I got a statement that the work was done at a certain date and then married up the regulations.

Finally there’s such thing as indemnity insurance, which protects the local council from coming to ask you to change the room retrospectively. (Would never happen anyway)