There is a program produced by Dimensions International, site at
www.dimen-intl.com.
Its called Flight Explorer and its a fantastic product, gives you live ATC data updated every 2-4 minutes.
It used to show everything over the UK and some of Ireland, western Europe, but now only the US and some other locations.
I imagine the reason that the UK switched off its feed is that they are producing their own version.
Anyway, for anyone interested in the US, or in traffic crossing the ocean (it shows up to 15W), its a great program. Also shows the flight plan.
Visit the website for more..