Unfortunately I think there's too much detail here I don't know to offer good advice, and to take a matter to court requires either proper legal knowledge, or a really black and white case.
If you go to court, then subject to the case being properly presented, the judge has to decide whether the installation date amounted to a binding term of contract because you relied upon it when entering the contract as per CRA2015, and then whether the valid defence of waiting on a wayleave means that VM can avoid paying compensation for the delayed installation. I think that CRA 2015 is quite clear that anything you relied upon becomes binding, and would trump any standard terms in VM's T&Cs, and if that were accepted (which it might not), the case then becomes about whether having agreed a contract they couldn't honour, they should pay compensation on the basis VM claimed they could service the property promptly. Maybe that would be in your favour, maybe it would not. The actual terms of the Ofcom automatic compensation scheme probably don't come into it since those are a regulator's code of practice, and not either case law or statute law, although they'd be a solid basis for evidencing what a reasonable daily amount is.
If I were in your shoes, I'd phone Which? Legal and get advice from them, but that's about a hundred quid a year and probably isn't a further expense you'd want to incur. Citizens Advice may be able to help for free, but this might be too complicated for them to cope with. Ultimately you may have to chalk this up to experience, take the paltry compensation offer, but remember that VM are not a company you'll want to do business with again.
As per the previous comments, would you be able to structure a claim that would be clear and refer to the main facts? Would you put up the case fee, accepting that this is money you may never see again, and that "odds" are unknowable? Have you got the time and the energy?
