For those applying to Jet2 here's some info from personal experience:
The money has basically already been outlined on this thread. In my opinion the FO salary is OK as a starting point and the Captain salary is low. The problem is that the starting salary is also the full salary ie. no payscales anymore. The payscales stoppped around 3 or 4 years ago. Pay is reviewed annualy but rises have not been forthcoming, perhaps unsurprisingly so with the economy and all. I wouldn't have hopes of a significant pay rise for SFO either.
This is all of course based on full time employment. There has been a recent HR drive to get as many as possible to accept part time. Part time would mean full time in summer and part time in winter or the winter off alltogether, with commensurate reduction in salary - great if it suits and you can afford it. Jet2 did say at the time that all future recruitment would be for part time contracts only.
As far as promotions are concerned, Jet2 does apparently have a promotion from within policy, although Direct Entry Captains are also sought (read into that what you will). The most recent promotions were for summer commands. FO/SFOs undergo command assessment and if successful (quite high rate of success I think) may be offered a summer command with reversion to FO/SFO in winter. In some cases it involves a temporary base change aswell, at the pilot's expense. I believe some of those that acheived a summer command this last summer may retain their commands, although it is unclear whether they had to accept taking the winter off in order to do so.
As far as basing is concerned, there are expansion plans mostly for NCL, EMA and MAN. I think its mostly 757 but MAN may also be for 737, so its a good bet recruitment is for any of those bases. Don't be surprised however if you have to accept dual basing. Yes that's right, being based in 2 places and being rostered to operate from either from one day to the next. At present this only exists for MAN and BLK. You would have a main base and an alternate base and Jet2 gives you an allowance for travel to your alternate base. Still it can make for a lot of time on the motorways in your own car.
As far as fleet/base transfers are concerned, there are extensive lists for both, especially for 737 to 757. Those at the top of the list get first consideration. That said, transfers are of course subject to commercial need. Fleet transfers are particularly rare as they involve expense and Jet2 is low cost.
Generally though, Jet2 is successful, profitable and growing which is pretty rare these days, and its a friendly place to work.
Hope the info helps and good luck.