'Boarding for storage' DOESN'T require council approval. Almost everything else does.
Quote 1:
> You can board out your loft without Building Regulation approval but laying or fitting loft flooring in the loft or attic must only be done to store light items, such as empty suitcases. If you mean to convert your loft into living accommodation of some kind then you need to find out from your Local Council whether you need planning permission. You will certainly need Building Regulation approval to convert your loft into anything other than a storage space. Please note, even if you planning to use your roof space as an office or study it still counts as living accommodation <
Source:
https://www.diydoctor.org.uk/projects/boarding-loft-with-loftzone.htm
Quote 2:
> I've received from my local authority Building Control Dept the following: "From our last visit, we would classify this space as living accommodation. If you wish to classify the space as for storage only, then you would have to remove any permanent staircase, any insulation within the roofspace and plasterboard finish. Otherwise, if you do not do these things then it is viewed that the space can be used as living accommodation." <
Source:
http://www.loftsandbasements.co.uk/how-convince-building-control-loft-not-living-space.html
Your friend should re-advertise the property as having an 'attic, boarded for storage', rather than a 'games room', 'bedroom' or any other sort of 'living accommodation' and invite the existing potential purchaser to submit an offer based upon the modified description.