If you go to court then you need to be very clear (and legally correct) on the basis of your claim in law or industry regulation. For a few things this is straightforward, for many things its not, and if you get the claim wrong, then you'll lose and not get the court fee back.
Rather than taking VM to court now, why not use the industry complaints adjudication scheme CISAS? That's lower risk, costs you nothing, its outcome is binding on VM if you accept it, but you can reject the outcome and still go to court if so minded. Also, courts expect that claimants have exhausted both the formal complaint route with a company, and then tried alternative dispute resolution (in context CISAS) before taking the matter to the courts.
So write up your complaint to VM, send it by recorded post, being clear on what the dispute is, what the evidence is, and what resolution you want. They might offer you a good outcome, we only hear of the instances where VM don't - although that's still too many. If VM don't settle the complaint on your terms, then you reply by reject their "resolution" letter and asking for a deadlock letter, and with the deadlock letter you take the matter to CISAS, where most customer complaints are conceded immediately, or upheld following a full adjudication.
