In the UK the channel number can depend on your provider (eg whether you have the default free to air Freeview or TV via a subscription provider such as Sky, Virgin Media, BT etc).
As for the channels themselves most are fully national, though some do have regional variations.
BBC for example is the main public broadcaster in the UK. Some of its channels (BBC Three, BBC Four, BBC News, BBC Parliament along with the kids channels (CBBC and CBeebies) are fully national.
The BBC’s 2 traditional main channels BBC One and BBC Two are mainly national but do have some regional variations, particularly in Scotland and Northern Ireland where a lot of programming is the same as in England and Wales but there are also noticeable difference (either in terms of different programmes altogether or programmes shown at different times).
Within England, the only major difference in programming are the regional news programmes - usually after the main news bulletins on BBC One.
The national (and international) news goes out as the ‘BBC News at Six’ between 6.00-6.30pm. This is then followed by a regional news programme between 6.30-7.00pm.
There’s also the ‘BBC News at One’ (1.00-1.30pm) and ‘BBC News at Ten’ (10.00-10.30pm) which are followed by shorter regional news bulletins (1.30-1.45pm and 10.30-10.40pm) as well as a few short regional bulletins during BBC Breakfast 6.00-9.00am.
BBC One also has regional variations on a Sunday morning covering regional political issues between 10.00-10.30am.
ITV1 has a very similar pattern to BBC One these days. Mainly national with a few regional news programmes throughout the day, but until about twenty years ago it was very different. Rather than the single, national company it is now, ITV (Independent Television) used to be a network of regional TV companies. They used to all make programmes that would be shown nationally and a lot of soaps, dramas, gameshows, live sport etc would be shown at the same time but because they were separate regional channels there was a lot of variation too. Each region had its own identity, presenters etc. it’s a shame that that has gone now.