Use the mini guide:
Watch live TV e.g. BBC 1 HD
Press Down Arrow (below OK button)
Press Down Arrow again (On my screen I now have info about BBC 2 HD)
Press Right Arrow (That then shows a list of programs for BBC 2 HD)
Press OK (Brings up information about the current program on BBC 2 HD without changing to it)
With thanks to J_Oz who posted this on forum.