V_2
At least we can agree that SEN-FLR is very likely to be one of the chosen routes.
The catchment population figures are not mine but those that have been published widely in relation to SEN, so I cannot vouch for their accuracy any more than I suspect you can challenge their veracity. I quoted the 60 minute figure as I think that is likely to make SEN as attractive to the potential traveller as other LON airports for any particular route on offer. The 120 minute figure is 19.3 million and that surely is the one you should be dividing by 4 "much bigger and better located/Accessible airports".
You really think EZY is an airline that would not "worry about yield" when talking about AMS? The SU95 may well fit certain routes better than the larger A319/320 which could provide the answer as to "why haven't easyjet tried it".