Area 20 is a large, diverse billing reference that is made up of an amalgamation of geographic areas — they're relics from all the different cable companies that eventually became VM. I live in Portsmouth, but area 20 also covers Manchester, for example. The fault affecting me is completely different to the faults affecting Manchester or any other parts of area 20.
I don't know why VM make so much of a big deal about these billing references when they're next to useless to the customer, but then with VM why should we expect anything different. Clarity and simplicity, why bother with that when you make things really, really complicated.
Anyway, you're much better off mentioning where you live or giving the first three digits of your postcode. Just be careful about how much info you reveal or the mods will edit your post.
"Cable broadband is typically faster than copper-based services, but a significant minority of users experience severe slowdowns in peak times." — Ofcom, UK Home Broadband Performance, November 2016
I think I'm going to go down the "I want money off my bill because i'm not getting the service I pay for" first and then leave when the offer period is over in a couple of months to be honest. I had no idea this issue had been going on for so long.