First since you where over 60 minutes late you can get a partial refund
Either print this or pick one up at the customer service desk in Heuston
http://www.platform11.org/passenger_..._intercity.pdf
Secondly this is in slightly limbo according to the internal timetable the 17:10 is deemed a type 'D' a outer suburban train (D841 to be exact) but its a mainline service (not intercity). That is rostered for a Cravens set and well they don't have a PA well some where fitted. Strange the 17:50 to Westport didn't stop to pick you up as it runs non stop to Athlone
The address you want Customer Services, InterCity, Connolly Station, Dublin 1.
For more instant relief I'd put good money on one Steve Murphy manager south and west standing in Heuston tonight, by all means have a go at him