According to benm345 "it has been reported in the media recently that aer lingus are looking to expand in the UK domestic market"
The only news report I can find is
Aer Lingus to bid for UK slots at Heathrow - Telegraph
Which is Aer Lingus...not regional. If Regional had the spare aircraft (which they don't), and IF they were to set up a base in the UK surely it would be at a stobart airport (Southend/Carlisle). If this was to happen it would be best be best been Aer Arran, as Aer Lingus has almost 0 name value other than flying to Ireland. Have a look at up the road Aer Lingus's LGW base collapse