Have a look
HERE, at the different options available.
The £10.50 service, looks to be the time limited one (ie: you get eight hours of surfing bundled, if you go over that you buy more time).
The Inter@ctive and Super@ctive seem to be the unlimited services, though obviously there is a price jump for both: £19.50 and £31.50, rising to £29.50 and £41.50 after six months, and remember for all packages you need to add £10.50 line rental for the phone service.
My exchange has been enabled, so will probably go for the Super@ctive package once I can cancel Ntl without penalty.
BW1967