I've just been doing some reading, and come to a conclusion.
Virgin are stuck.
From my understanding of how the network is laid out, the CTMS for me would probably be in Watford... so it's probably covering quite a large area. That's not a problem, but the network is going to be rather loaded. There's a fixed number of frequencies to shove my data into, and as they're shared, they're filling up rapidly. Surely the only way for Virgin to get around it is to split down the network into smaller chunks, and install more CTMSes at the regional headend. That would probably require splitting out some of the main fibres running to Watford, and running even more. Plus all the extra infrastructure needed to connect everything up. Do that across all the headends, and it'll cost a fortune.
So rather than investing - like every other ISP - they're squeezing for all their worth, and basically milking what they have. They probably have no money to invest in networks, and nobody will give them money to invest, so rather they're taking a short-term view of headline-grabbing speeds, and pulling in customers. That explains the minimum 1-year contract, because they know full-well people will probably want to flee when they realise it isn't what they expected; plenty of ADSL ISPs with decent networks have very short contracts because they CAN deliver the product. Just as I left Be, they announced a massive network investment.
Trouble is the VM network is a hodge-podge of networks, and just has not scaled. It was all designed for analogue, and not only that, it was designed to be a small, local network, serving the area it served, with the services it had. I wouldn't mind betting there's a group of core network techs trying to make the best of a bad thing. I'd love to hear their view on it, but I bet they would soon find themselves staring at a P45 if they did.
It's a crying shame, because VM probably have the capability to make the network something really great, but probably no money to do it.
That's my view, anyway