Re: <interesting> <exciting> oh <sigh!>
"Virgin is available but it appears expensive to me."
If the household is fighting over a miserable 6 Mb/s then I'd suggest you have another look at Virgin, and in particular pricing your full service like for like (so phone rental, phone usage packages, broadband). I've been on cable for over fifteen years and dumping BT for Telewest/VM was one of my best decisions. There's often some good sign up deals, and when your discount runs out you can negotiate an acceptable price with their sales retention team. Obviously avoid anything you don't want in the bundles they push, but IME the broadband and phone work reliably and well, and a particular benefit of Virgin cable (over BT) is that the occasional technical problems are resolved effectively in acceptable timescales.
A quick check suggests that (ignoring introductory discounts of around £6 a month) you'd be paying £39 a month for phone including "unlimited" weekend calls, 50 Mb/s broadband, and the basic TV service. If you just wanted broadband its about £28, and as a standalone that starts to look pricey, but why would you want to have a BT landline and separate cable broadband?