Couple of thoughts.
There are many ‘pest treatment’ companies that I would think could treat you garage in a manner that it worse than ‘uninteresting’ and so alleviate your ‘thing’
Secondly, you could consult a builder to create a ‘temporary’ room within the garage that can be assembled and dis-assembled, which might not then contravene planning approvals and is in ‘your airspace’ and not affixed to common property floors or ceilings.