Very useful! Of course, in Yorkshire we don't use 'sit/set', so there's no confusion.

Yorkshire dialect insists 'I/you/she/we/they were sat...' wherever and whenever you apply it.

So remember it's:
'I were sat at t'table this morning.'
'He's sat at t'winnder (aka "window") nah (aka "now").'
'They'll be sat in t'car tomorrer.'

Confused? You ought to hear broad Yorkshire kids trying to 'talk posh'.