I picked up a leaflet at my local railway station in Cumbria this morning about the tours from Oban to Mull, Iona, Staffa, Lunga and the Treshnish Isles.
Booking is now open for the whole year with West Coast Tours.
https://westcoasttours.co.uk/faq/
(they are the tours arm of the local bus operator- West Coast Motors).
In particular note that Oban to Craignure is now a 2 boat service (with the 2nd boat, the Loch Frisa, being a much smaller and simpler appointed ship).
This means that the ferry timetable has been recast and morning departures are now 25 minutes later than hitherto, with afternoon returns also adjusted. All the tours use the big ship, not the Loch Frisa.
Although there is an Iona Tour this can be done cheaper on your own, as a service bus to Fionnphort (and also one to Tobermory via the Fishnish ferry) also meets all 'big ship' arrivals at Craignure and Tobermory. It is not yet clear whether service buses will also meet the Loch Frisa sailings as well.
For the Isle of Ulva public transport users should use the 0955 ferry from Oban, the Fionnphort bus as far as Salen, and then Ulva Ferry Community Transport-
https://ufct.co.uk/timetable/
EDIT- The Bus Timetables are now issued for the Summer. There are extra buses for the Loch Frisa sailings between Craignure and Tobermory, but the service bus to Iona is now reduced. To do Iona independently you now have to be on the 1st ferry from Oban. The 2nd ferry you have to be on the tour bus.
See services 494, 495 and 496 on this link (494 is Tobermory to Calgary)-
https://www.westcoastmotors.co.uk/services