Sony KV28 - why is image larger with Telewest?

Changing from terrestial bbc1 to Telewest bbc1 I notice a significant
increase in people's head size although the 16:9 image has no black bands.
The TV format setting is widescreen 16:9 and it makes no difference whether
this is sub menu set on or off. There is no image edge stretching apparent

Could it be that the Telewest scaling is different? Heads seem too big. .

I'm not familiar with any set up of the Pace decoder. If there is a format
setting then I cannot find how to access it from the handset.

Beemer