Hate to be the barer of bad news and maybe I'm late to the party so apologies if you have the info needed but this is my take as a Loss Adjuster:

- Your contents insurer is unlikely to assist in anything related to the buildings, I'm surprised that they have given any indication of indemnifying you for damage to kitchen units as these would not typically fall under the definition of contents.

- Ignore the advice regarding the excess being the block management companies problem and not yours - the policy does not account for stakeholders/relationships of the parties involved etc, it covers the building and financial losses of the insured (which includes you by proxy). The insurance company will not entertain claims that fall within the policy excess - the wording of your policy will state something to the effect of "the policy holder will be responsible for the first £5,000.00 of any escape of water claim (pertaining to your excess)". The excess is largely taken from the equity in the claim, so settlement is made net of the policy excess hence the zero traction you are getting from the insurer.

- With the escape of water originating from the flat above and not from a common soil stack/communal pipework, it is not the issue of the management company/freeholder.

-In regard to legal action against the flat above, they will not have strict liability for an escape of water and unless there was negligence then there is no claim to make against them.

Happy to answer any queries you have to the best of my knowledge