The latest update message from VM says '..an engineer is on their way. The estimated repair time is now: 11/04/2017 14:00:00', which is very precise for something that is expected to last at least a week..'
Got a pop-up offering to discuss this on Live Chat, but it won't work (because the speed is too low?).
How do I register a formal complaint and apply for compensation?
Formal complaint channels are as per "contact us" VM forum team will try to help with technical issues and may be able to get some more info on the fault, but this is not a "formal" contact route for contractual matters. You may be better using good old "snail mail" if you want a written response?