It has been some years since there were sailings in October. The company continues to operate its long-established pre-Christmas and post-Christmas Dublin sailings.
Sailings ex Dublin (Terminal 1 i.e. where Ulysses sails from) are at 0100 on Sundays 16th and 23rd October. Also 0100 on Sunday 18th and Tuesday 27th December.
Sailings ex Douglas are at 19:30 hours on the day preceding all of the above dates. The passage time on "The Ben" is 4¾ hours.
Am mentioning this here in case it's of use to anyone for taking a short break/trip to the Island. The steam railway is still operating as is the Manx Electric Railway and the homeward trip can be made by sea via Heysham or Liverpool (a through sea-rail ticket Douglas to Holyhead can for instance be purchased but good idea to check prices as Douglas-Heysham/Liverpool sea ticket then a SailRail ticket then Heysham/Liverpool-Dublin via Holyhead may be cheaper) or by air from Ronaldsway.
There is a Dublin Bus at 20:00 hrs from Busáras that one can avail of (euro 2.50). It's the bus that connects into the 20:55 Ulyssses sailing to Holyhead and will mean a long enough wait but having done it myself some time ago, the time will pass and one can observe the shipping movements from the public area outside between the terminal and car park. There are hot drinks machine/s in the terminal. The cafe upstairs probably won't be open but am open to correction on this.
Alternative is a taxi from the city centre which can vary from 11 to 15 euro (approx.). If arriving into Dublin at 00:15 ex IOM a taxi is a must and would be a good idea to pre-book or have the number of a few firms written down/saved to 'phone. There is car parking available adjacent to the terminal too (unsure of cost).
Anyway posting this here in case it's of help to someone.