r/Glasgow Tools

I own a ground floor tenement flat and have been here for over a year. The cupboard space under the close stairs is locked and I have never had a key. I can see some items are stored inside it by squinting through a small gap (ladder and brushes I think). To the best of my knowledge it has not been used by any of the existing residents since I moved in - I have had a note up in the close asking for info and also I've put my own padlock on the door for a few months to see if it caused any issues but nobody has said anything.

I would like to use this space to store my bike and maybe a few other items as it is secure and sturdy so there's no security concerns. In order to gain access I would probably have to break the door and get a new one fitted (the lock is an old style mortice type thing).

I checked my property deeds which states - that my property is -
“Subjects within the land edged red on the Title Plan being the first house on the left hand side of the Tenement. Together with the coal cellar pertaining to the subjects in this title situated on the ground floor underneath the staircase leading to the upper floors”.

If anyone can advise or give an opinion that would be great:

Does this mean that I own this coal cellar out-right or is it a shared space?
Would I be within my rights to engage a joiner/locksmith to see about getting quotes to gain access and get a new door/lock fitted?
Should I involve the property factors, solicitor or anyone else?

Thanks