OK, to sort out the problem of why uk internet is more expensive you have to look at the infrastructure of the network, namely that the US is mostly fibre optics and/or has been digital exchanges for some time, where BT only really updated to those systems in the 90s, before that it was mechanical exchanges (dont ask!) So there networks are more upto date before they start.
Local call charges are none existant over there, so ISPs originally had no method to provide competition, so they resorted to upping the bandwidth limits, improving quality of service and such, where in the UK, companies had to pay high call charges, then down to local rate, still 60pence an hour, then down to 0800, which costs more than that, now to friaco. its a long transition from £1.20 a minute + isp cost to the current £6.99 a month for unlimited. So the introduction of broadband had to wait for these transgressions to fizzle out before the telcos would actually update to digital. It will take a few years yet for us to catch up the rest of the internet big players, simply because we were so far behind to begin with, theres no reasons other than those why we pay alot more for the services we get, and why its poorer service than other countries.
For a contrast, look at mobile phones, in that respect we are ahead of most of the world, simply because it didnt catch on in places like the USA as it did here, we're a nation of "fad" people, if its "in" we want it, so thats why we're heading into the 3G era, and the US are lagging behind in tri-band, as are alot of europe.
Every country has its downfall in technology, unfortunately ours is the largest thing in the world
well... need i say more, we invent something then become crap at it... (Football ;-)