Live TV on xbox360 extender

In the UK TV is PAL which is 50hz, as standard the 360 will put out
720p@60hz, this means some pretty bad image quality as the 360 appears to be
doing a pretty poor job at upscaling from 575p@50hz to 720p@60hz.

Now the quality is much better if I switch the HD cable so it's ouptut
575p@50hz obviously I loose all HiDef material, also this isn't really a good
solution because the 360 must reboot when switching.

So my question is, is it possible to switch the 360 into 720p@50hz if not
for games then at least for media centre?

I've tried this question in several places and even rang the 360 helpline
with no luck, hopefully someone can give me a pointer or is there xbox360
intended as an extender only for U.S NTSC regions?

Regards

Slingshot.