I'm fairly sure that, in this period, Scottish and Grampian did not routinely show religious services on Sunday mornings - unless either station was the actual 'host', which STV obviously was on this occasion.

With rare exceptions - Easter Sunday or if Christmas Day happened to be on a Sunday - it was the same with Ulster, and they didn't take a regular place on the rota until their much-heralded OB unit was in service from early 1982.

Found it
6th November 1977

I bet it wasn't just children in the vicinity watching "The Fantastic Four" given the competition on BBC1 was "Trade Union Studies"...