Legally now they could probably operate them on behalf of Aer Lingus UK…
Cozy F]Indeed
I believe the issue with Ryanair was scale, they wanted single token aircraft on their UK AOC and then have all the other UK Domestic and UK Non-EU flights operated by wet-leased aircraft running to hundreds of flights a week. The Secretary of Sate can, and will, approve temporary waivers, for short-term capacity, but the type of operation planned for Ryanair UK was way outside this scope.