As mentioned the cable network is physically designed for downstream broadcast not upstream ip traffic. There is a very limited amount of upstream available so giving people >512 could quickly flood it and everything would grinde to a halt. I think later DOCSIC versions have better support but without replacing ALL the network hardware you aren't going to get huge uploads. If you wanted to switch the entire cable network to an ethernet based system you'd have to have Gigibit to the house socket (very expensive!

), cable at the moment is delivering something like >150Mb/s to your door, including all the TV etc services.
Besides it's NOT a business service! If you want to flood my home network with your server uploads go get a business service, NTL will happily sell you one (I've used them before, cheaper then BT

).
As to the 2MB upgrades, from the last stuff I heard from NTL it looked like they'd changed there package lineup for next year to be;
- 10Mb, 75G/m cap, Broadband+, £34.99
- 2Mb, Unlimited, Broadband+, £24.99
- 1Mb, Unlimited, £17.99
This would make more sence as it's less confusing then adding another 2-3 tiers and there current network isn't really upto switching everyone to 10Mb, but heh when have NTL made sence.