TSR - yes, I stand corrected, no 738s in public service before 98. 734 would sound about right, either way, the flight was all but empty - it was December, and I don't think TK were pushing IST as a hub as much as they are now.
So back to Jet2 - surely they applied for the slots at IST before putting the route on sale. After all, if they weren't happy in their negotiations, they could have used SAW like other budget airlines, they didn't need to use IST for connectivity, even if it is a better airport for access to the city (imho).
They seem to have backtracked without even giving it a try.
As for WW v LS - I have no loyalty to either, but it was obvious which airline was making money and which one wasn't. BE have already picked up some of the EMA scraps, clearly there were some routes that were more suited to their business model, I don't really see BE and LS as major competitors.