Now broadband TV

Now may block your port into the internet, since you do not pay for the internet access option of Now.  Also Now alone is using 3/4M for video streaming so Now's internet access may not be better than your IMS.

For technical only, Now's modem to the Set-top-box is already on IP. So all you need is to connect a router/switch between the modem to the Set-top-box. ie :
Now's phoneline ----> Modem ----> Router/switch ----> PC and the Set-top-box