Well this doesn't sound very promising. I guess I'll just have to keep trying with the managing agent and freeholder's agent. Any advice on that would be appreciated.
From my own experience some 7 years ago and taking account of legislation changes in the meantime, I agree that the management and freeholder's agents will be where you will need to apply the pressure.
Ours was a 4 dwelling unit which was a completely refurbished and renovated former industrial building in the far reaches of Cornwall. The management committee was comprised of the dwellings' owners, and the management company was the plot freeholder. Copper was the only available option at the time of renovation, but it was all ducted and made running the fibre into the building very straightforward. Cornwall Council was ahead of the game in getting high speed internet established, and when the fibre rollout started in in our neck of the woods, it didn't take me long to realise that we were being bypassed.
I was at a bit of a loss as to how to deal with this initially. but the good folks on this site got me pointed in the right direction, namely our local BDUK organisation, Superfast Cornwall. After a slow start, they really came good and pulled in Openreach who surveyed the site. I signed off the wayleave on behalf of the management company, and the fibre got run in.
Ironically, by this point, my wife had got fed up with life in a flat, and I (very) reluctantly agreed to move, so didn't feel able to pursue the switch to fibre as it would have risked a substantial payment for the unused portion of the contract. The new owner will have had the full benefit of my efforts!
One aspect I didn't have a chance to get to grips with was fibre distribution within the building. Unfortunately, the telephone lines to the individual flats had not been ducted, and pulling fibre through was not feasible. With only 4 flats, and the new much more flexible fibre starting to become available, it was probably not a major problem, but for your situation, with 7 floors and 41 dwellings it may need careful consideration.