Following the merger of Tmobile and Orange in the UK (to Everything Everywhere)

From 5th October 2010 you can jump networks when you don't have a signal.

Really does maxmimise your network coverage by utilising both networks and it's a free upgrade.

Taken from Tmobile website:
Fancy talking and texting in more places than before

Now you can sign up to pick up a signal from Orange when you don't have a T-Mobile signal so you can call and text in even more places.

TmobileCustomers Sign Up Here:
https://www.t-mobile.co.uk/share/

Orange Customers Sign Up Here:
https://kareena.orange.co.uk/share/

thanks to digicom on another forum