Hi Joasis, firstly - comiserations! I had a very similar problem, same set-up, different (known) freeholder. In the end I got so frustrated, that I sold the flat and bought elsewhere in HOP. Having spent a lot of time and money doing up that property, I just couldn't stomach having constant negligent behaviour from the tenants above.

You should have contact details for the freeholder and the second leaseholder (in this case the same person, if that is correct) in your leasehold paperwork, which your solicitor should have checked when you bought the property. I would try to direct written communication towards the actual freeholder in those documents, and if that isn't working I would consider forking out a fee and get a solicitor to write to them. In any case, make sure you document everything, with photos, times etc. Leases vary a lot, but both you and the other leaseholder, who is also the freeholder, if I understand that correctly, have a duty to keep those parts of the property they are responsible for in good working condition and above all, safe. If her tenants are putting the structure, or you, at risk, then that is probably your best angle. But it can be a long drawn-out process... Very sorry not to have anything more positive, perhaps you'll get a reply from a solicitor here on SE23. All the Best!!