Aer Arann rotate aircraft around different bases quite regularly, one aircraft will probably operate for a few weeks before being moved. It looks like an ATR 72 will operate the first few flights before switching to the ATR 42.
Aer Lingus have regular advertising campaigns in the UK, radio and newspaper adverts are almost constant and SEN has been included. There was a flashmob promoting the new route, the SEN YouTube account put a video up.