The Sky viewing card allocates your local ITV service to Channel 103. You can't change which service you get on 103 and you can't add another numbered channel to the EPG (electronic programme guide) to view ITV from a different region.
However, if you're prepared to do a bit of fiddling about, you can store a different ITV region as an 'other channel' (which means one that's not listed in the EPG). You won't be able to view it by selecting a channel number but you can get there by going to Services > Other Channels on your screen.
See here:
http://www.stevelarkins.freeuk.com/itv_regions_sky_digibox.htm