The channel numbers in some cases may differ in your region from others - for instance in Wales there is the requirement to provide S4C from some of the transmitters.
If you get the Daily Mail (may well be done in other papers) the Freeview, NTL, Sky etc digital channels are shown above each set of program listings i.e. Channel 6 for ITV2, Channel 7 for BBC3 and Channel 10 for BBC Four in the case of Freeview.
The TopupTV channels are displayed but, unless you pay a subscription, you obviously can't watch the programmes. To be frank the coverage is too skimped during the day to make it worth it.
Don't forget that unless you have a wideband TV aerial you might not be able to pick up the intermediate channels in the 30-40 or so range.