To respond to one of your initial questions:
The whole procedure for Dublin departures operating low-level has changed recently with the change in bases of L975 over the Irish Sea. It used to be the case that Dublin would transfer traffic to the Scottish IOM sector, who would work it (mainly inside controlled airspace, as the bases used to be relatively low, so very little traffic actually left the base of the airway.) Now that the bases have been raised somewhat, the new procedure is for Dublin to transfer traffic at FL120 and below to London Information (as was the case in your specific example.) However, London Information are then supposed to contact Scottish IOM sector for a clearance to re-join CAS. I am a little confused as to why this didn't happen in your example, and you should, in my opinion, have been given further routing (along with your clearance) from London Information. Who did London Information transfer you to after they were finished?