The Sea Kings from the SAR flight at Gannet (from 771 squadron based at, um, Culdrose) are a fairly common sight over Glasgow - though not usually at low level.
They sometimes make hospital/organ flights, and I have seen a Sea King or two in the car park of the SECC - too big to fit into the adjacent heliport!
With it being back to school/college time, it might have been doing a display for folks at the Nautical College. Maybe there's a PPRuNer here at Gannet who can provide more info.?
Here's their RN mini-site:
HMS Gannet