Hello I am a lawyer with over 15 years experience. I will try to help you with this. Have they caused any damage?
Thank you for that I will answer you later this morning.
I am sorry for the delay. I have had some things come up this morning but I will answer you this afternoon.
If the garden is yours and the contractors have entered it without your permission then they are indeed trespassing. If they are trespassing and do anything intending to intimidate, obstruct or disrupt lawful activities they would be committing the offence of aggravated trespass. That doesn’t seem to be the case here. In the absence of any damage it is unlikely that any offences have been committed and iut I sunlikely that the police would be willing to get involved.
It may be that there is something in the documents around your purchase of you property or in the land registry entries giving other people in the building the right to enter your garden to effect repairs Do you know if this is the case. Also usually in a building where there are a number of flats maintaining the roof is usually the responsibility of all the flat owners. It seems curious that they have not discussed this with you.
Assuming that there is no right of access in terms of civil remedies you could demand that they remove their things from your land as they do not have your permission to be there. You could go to court to seek an order requiring them to leave and seeking compensation. But these would be very costly and time consuming activities which would not be very effective (proceedings would probably take longer than the building work and the compensation would be negligible).
I can quite understand your irritation with this rudeness on behalf of the builders and those who employ them. But in terms of legal remedies for the reasons set out above I don’t think there is any effective legal action you could take. It may be that you could remind the owner of the top for flat that it is yours and that she should have asked permission first and if there are particular things you want to change (eg to do with time of works or noise etc) you could ask/tell her to ensure these things are done.
Legally though you are in a position where you are being wronged but largely because the harm and losses are not great there is very little you can do to practically enforce your rights
I hope this answers your question but please feel free to ask follow up questions. I would also be grateful if you would please rate my service. This will not close your question and I will continue to answer.