[nwtv2003]

One thing I have always wondered about ITV region branding is why ITV hasn't considered licensing the ITV1 brand to STV/UTV to make it a national brand. Surely, it wouldn't be too difficult to have a voiceover say something like "This is ITV1 via STV" or "This is ITV1 via UTV" on idents, etc., would it?

As stated I think STV value their own brand and independence over ITV. However when Channel TV wasn’t owned by ITV plc, it still adopted ITV1 and ITV News branding for several years. But in Channel’s case it was probably a matter of cost saving, certainly on the ITV1 branding front. 

The closest there’s been to a true network identity was the 2002 celebrity idents which were adopted by UTV and Scottish and Grampian as they were. In UTV’s case they didn’t last long.