Heard of Virgin Media? That has On Demand from 4, ITV, the BBC and others.
...it also requires a subscription, and for you to live in a cabled street, and Virgin currently have no plans to expand their footprint.
Or BT Vision, that has TV Replay for the five main terrestrials.
Likewise, requires a subscription even when 'catch up' is available free online.
Which is why Apple TV would be awesome with iPlayer et al on it. No subscription required, and nothing but a broadband connection.