Can't see Jet2 been the slightest bit interseted in starting anything global from London. If they don't fly short hall from STN why would they go long haul from STN.
Jet2 has its roots in the North and any expansion into long haul is probably going to be from one of their Northern bases. Blackpool anon starter and Leeds would be tricky but it may well work from Manchester or Newcastle where they already compete on many routes with other airlines. However as they are having trouble aquiring suitable 757s for SO7 I can't see any expansion long haul for a while. Stansted though is simply wishfull thinking and based on no firm logic as to why a airline with an excellent network in the North would suddenly open a base in the London area to do simply long haul. If they do use a London airport it would be more more likely to be Gatwick which is where their Manchester and Newcastle domestic operations fly into.