Alistair
the answer is no, LOCHFYNE rested on the sabbath.
Apart from the early ABC ferries and SANNOX, in winter sundays the only thing moving on the firth was CALEDONIA or TALISMAN giving one run down to Rothesay and back calling at Dunoon around 6pm, which I used to catch on my way back to Liverpool.
That was the last boat out of Dunoon for a Sunday.
                                                                           Sandy