Purely speculation
People have assumed this STN/SEN rumour is based around Brexit. Another hypothesis is the fact that a major British regional carrier appears on the cusp of collapse and there will be a crop of key airports willing to make deals with airlines able and willing to fill the gap.
ots safe to say the EZY have london very much covered and operate out of 4 airports. With flybe gone, the likes of MAN would be on obvious place to grow and the likes of BHX would be a tempting new base to set up ...not to miss the likes of BHD and GLA/EDI wanting/needing to plug the gap. We already know that EZY applied for BHX slots to operate AMS/CDG/MXP/TXL/NAP in addition to the new BHX - GLA/EDI routes they’ve added but weren’t able to follow through or find the slots... the intent however seemed to be there somewhere in ways head of EZY HQ
The loss of flybe represents a massive opportunity for EZY/RYR and the winners at the ones who can grab the routes fastest. For that you need to spare planes.
Just a thought...