Soundproofing low ceiling

I live in a converted Victorian school. The impact noise from the flat floor above is terrible. It's actually a relatively new floor (upstairs) but the owner of it is a nightmare and the company who fitted it are complete crooks. The result is a constant creaking/cracking (up to 70db!!) every time someone just walks in the flat upstairs. He is refusing to do any repairs whatsoever - despite having been to court over the issue. He rammed boards between the joists and used cheapest chipboard for floor. Result = creaking, popping, cracking. The noise is very much coming from the existing structure of the floor upstairs, via flanking. Needless to say the freehold are absolutely useless also.

I've attached a floorplan of my flat - in the non-bedroom part there are high ceilings and I think I can easily manage to install a false ceiling there (I have at least 10cm to play with there). However, where the bedrooms are the ceilings are very low and I only really have 5cm to play with. On top of that there are 2 RSJ's running across the bedroom areas - that are boxed in and will therefore cause a break in any materials. It's a nightmare!

I am desperate to find something that will help in the bedroom area. However, I am unsure of what to go for having read around? ....atm the ceiling is made up of 2xlayers of plasterboard screwed into the joists directly.

Can anyone recommend anything on top of this? That would be effective for such loud creaking/cracking.

I am only interested in reducing impact noise from above (as I know the airborne will naturally be reduced if I can sort this).

Does green glue actually work if I put 2 more layers of plasterboard??

Does acoustic plasterboard actually work?

What about MLV on a ceiling?

Or should I be looking at soundproofing wallpaper foam and then a layer of plaster?

What's the slimmest best solution? Perhaps resilient bars are an option straight onto the ceiling as is - and then one more layer of something? Do you have any experience of this?

Grateful for any thoughts - or for anyone's experience where a particular material hasn't worked.

Many thanks,