I'm sorry Skipness, I think you are missing the point and still seem to be fixated on the idea of bases. Ryanair don't need to have all of their aircraft, or any of them in fact, on a UK AOC to fly between the UK and EU, regardless of whether many of their aircraft overnight at Stansted. easyJet could, in theory, base aircraft at an EU airport but they would only be able to fly from that airport to the UK, not to another place in the EU. Hardly worth them bothering as they can do the same with UK originating aircraft.
The rights are reciprocal. The EU (as a whole) is one market and the UK is another. Operators from both sides can fly between one block (market) and the other, but not entirely within the other party's block. The EU is a much larger 'single market' than the UK of course, which makes it seem that EU operators are getting a better deal. But it is definitely not the case that the UK grants privileges to European operators that are not on offer to UK operators in Europe