I’m a town planner who works in Scotland. From the information you’ve given I would advise that, from a planning perspective, your factor is incorrect and that you do not need planning permission for letting out one room in your flat on a short term basis.
Glasgow City Council have developed local policies on various types of hosing need. I would encourage you to read this document - especially Section 4B:
Paragraph 4.13, which covers flats and short term renting, is directly relevant to your case. It advises:
“Planning permission is deemed not to be required where only one lodger is accommodated in addition to one resident family.”
I would suggest refering your factor to this guidance. You could also approach the Planning team at the City Council for confirmation.
This is only the planning perspective and there may be other controls, such as your conditions for your building. The Scottish Government are also looking at creating further regulation of short term rentals so the situation could change nationally very soon.
I hope this helps.