Interesting Mr Nutter that you should discuss uncapped services especially when the current trend in ADSL provision is towards capped services due to BT increasing / changing the way they charge for backhaul bandwidth. Wanadoo, BTBroadband, both going hard capping, other providers 'looking closely' at it.
BT have no intention of introducing anything over 2Mbit at the moment at all - there is still no Home 2Mbit product, these are all based on Office products, and no rumours or announcements on an Office service over 2Mbit have been heard. Any increase in bandwidth will come from Bulldog increasing the reach of their network, this will be far from national availability though and will probably only be the inner cities / larger towns.
As far as 800k upstream goes have heard absolutely nothing at all about this one, Bulldog offer the highest residential upstream at 400k. Increasing this to 800k will limit availability of the services somewhat (as unlike cable ADSL is a distance dependent technology, if you're too far from your exchange you aren't going to get service or will be limited in the speeds you can have). Also ADSL can't do 800k upstream
Maxes at 768k-ish.
Sadly from your point of view unlimited services are slowly but surely becoming less and less available and capping more common place as companies try and consolidate and 'reign in' users using 3 figures GB per month.
NTL are by the way the largest cable operator in the UK by a fair margin.