UK Landlord Forum / Life

Hi I'm New to the forum.
My story is long and drawn out and whilst as much detail as possible has been requested i'll try to keep to main points.
I purchased a leasehold flat above a commercial premises in 2017.
Service sharges are ad hoc, depending upon when repairs are carried out. This is split 3 ways as there are 2 other flats in building.
Problems with damp and water ingress soon became apparent.
The lease states the roof is the freeholders responsibily,
Repairs took place to the roof in 2019 for which a sum of £5000 was charged to myself. (Roof Repair charges are split between myself and commercial premises below.). I paid in full.
Soon after, the water ingress reappeared, causing significant internal damp and subsequent damage to walls plaster, paintwork etc).
The management company ignored requests and pleas to deal with the issue.
I then received a bill for £2700 for further roof repairs, I was unaware of.
I held off paying this (there was no consultation that repairs would be taking place) until sure the issue was actually repaired.
It wasn't.
The problems remain and the internal damage is so significant my tenant left the property.
When I finally decided to pursue a formal complaint with the management company, they did not respond within the timeframes given in their policy.
I then tried to refer to RCIS to find they were not registered (although they claimed to be).
Whilst trying to unpick this (lot's of ignored emails, promises to get back to me, relevant people unavailable ) I was informed the management company had been changed.
They had clearly avoided dealing with my complaint as they were aware this was coming.
New management company paid lip service, came out to survey the property, then sent me  a bill for the £2700.
I explained the dispute - they have ignored me since.
I got a letter from the freeholders solicitor, semi threatening to take legal action but also claiming to wish to seek a mutual resolution. (october 2024 tried to attach but unable to)
I responded immediately and have since sent several emails following up, to once again be kicked down the road (awaiting info from previous agent etc, etc, etc).
I have now found a buyer for the property and am keen to sell. I have been transparent with the buyer and reduced asking price by £15000 due to roof and subsequent internal damage.
The managing agent and solicitor are yet to release the management pack (deliberately It seems) Stalling the process. I am happy to agree to settle the outstanding from the proceeds of the sale, in order to keep things moving but I still dispute both the charge and the mismanagement I have been subjected to.
Is this a case for the first tier tribunal? is it worth me pursuing? If so what are my first steps?
Thanking you in advance for any advise you can give and promising not to be a 'one post wonder!'