How do I change the TV region in the settings

My ITV3 seems to have moved and I've got some channels don't seem to be from my Region. When I do a new channel search there's no mention of region although I do feel sure that our region was mentioned when I first set up the box. So my question is how do I change the TV region in the settings?
[If I'm still blocked by the OP I'm wasting my breath. But here goes...]
If it's anything like a 2000T you can't.
What you can do is manually scan the correct frequency (for ITV & ITV3) for the transmitter in your region. If that doesn't match the currently stored value for LCN3 (ITV) then the Humax might give you the option of select region. I've just manually rescanned my Humax. Having stored the East Midlands multiplexes I added West Midlands and Yorks&Lincs BBC/ITV muxes. On each scan the Humax gave me a choice of region. I chose East Midlands and the extra BBC1/ITV for W Mids and Yorks were put up in the LCN 800s. Not sure this will work correctly if you have the wrong region stored in the first place.
Ta Daaaaaaaaa
For anyone with same issue - I actually retuned the channels WITHOUT the Smart switch
I had to reset my recording schedules but noticed all the channels were properly refreshed, ITV3 gone back to 10, load of new channels and load of new Channel logos (not sure how long I've been missing these)