If VM do install and you consider them(i advise agains it) make sure you do research on their community forum before picking them, ive been with VM for a year and have had both terrible customer service and terrible internet connection from them. High jitter and massive ping and tons of packet loss to servers less than 50 miles away. IMO a terrible ISP they claim BIG things and provide very little of them.
Go for Zen. I've been through a few ISPs and Zen has been the best by far. I was tempted by Virgin but when I compared reliability, customer service, etc they fell well short. You can get 100gb for 35 per month which is within your budget. I live in Willesden btw.