AFAIK the only certain information on the upgrades is that all ntl cable 1Mb and 2Mb accounts will be upgraded to 10Mb by the end of 2006, and all 3Mb customers should be on 10Mb now (don't know if they actually are). All 10Mb accounts will be capped.
So the only way to upgrade to 10Mb ATM (unless you're lucky - don't know if anyone on the 1 & 2 mb tiers has been upgraded yet?) is to subscribe to the £37.99 tier.
If you go to the
speed upgrade page, you can check what speed you can be upgraded to: if the result is 10Mb, then you can get 10Mb, if the result is bund03, you're still limited to the 3Mb service. As I said, though, ntl were reckoning that everyone on the 3Mb tier should be upgraded by the end of 2005.