Manchester Helicopter Charter Company used G-BPAI primarily for pleasure flying from their base at Manchester Barton around that time.
Apart from Barton, they would operate pleasure flights from pub gardens in the summer.
Are you sure the snaking river is not the adjacent Manchester Ship Canal which runs alongside Barton aerodrome, and your 'pub' was in fact the clubhouse restaurant ? There are also a few hotels further along the canal which host helicopter visitors.
A colour scheme might also assist. BPAI is predominantly red. The reason I mention this as one of the MHCC shareholders had another Bell 47 at the time in an ex-Army overall paint finish, should that jog your memory.