To keep up with any developing riots, one way may be to sign up to twitter or other feeds on police force websites.
You can find a link to your force website via the national site http://www.police.uk/
For exmple to follow the Met online, you can register with their news service –
http://cms.met.police.uk/user/register
There are besides for London the communitysafe website http://communitysafe.gov.uk/ and the LISTEN group of London security and building managers.
As for 24-hour news channels, you can follow the BBC or Sky –
http://www.bbc.co.uk/news/uk-14449675
http://news.sky.com/home/uk-news
http://news.sky.com/home/uk-news/article/16046136