We used Dublinairporttaxis.ie for a meet and greet transfer at the Dublin airport to our Hotel ,transfer to Heuston Station and back to our Hotel, then back to the Airport. This went without any problems and they were very professional drivers. I arranged this all online and payed after all was done. Ask by email or phone for John Millington he's great to deal with. They keep up with any changes I made
and confirmed that they got the changes by email. I would recommend a phone as I used my iPad so communication could only be made with a wifi hotspot etc.. Very reliable.