The data stats above are not entirely appropriate to use for comparison. It shows the number of applications sought and if you didn't apply for one, you wouldn't be listed even though you might well have subchartered a foreign-registered aircraft more. I find it very hard to believe that the figures for some charter operators are so low.
If this is correct, how come the EuroAtlantic L1011 and White A310 spent so much time at LGW this summer working for FlyJet (who don't even appear on the list) and other major airlines? I wouldn't base any serious argument on this list. It all depends on how diligent the airlines are at applying for the waivers, and there is no process to ensure that they obtain a waiver for any instance of using a foreign-registered aircraft.
Playing Devil's advocate, it also doesn't show how many sub-outs for other European airlines that UK airlines have undertaken this summer. In the case of Titan Airways alone, I suspect it's a fair few. If we are moaning about "flagging out", then it would be unfair to forget this section of UK industry which seems to do quite well out of the ability to "flag out" in other countries. It does cut both ways.