After talking to a friend who works for Jet2 this is the deal as it was explained to me. The scheme applies to non-type rated pilots and is designed it would appear to expose Jet2 to zero risk (which begs the question why they have people enduring numerical,verbal reasoning and psychometric tests and then a simulator assessment with CTC).
You have to raise £20000 to pay for the rating. It's up to you how you raise the money. However any loan is in your name so if anything happens to Jet2 during the repayment period you're saddled with it. They only pay back £20000 over 3 years and not the interest on the loan which can be a substantial amount depending on the rate you manage to get (for example with a highish 9.9% APR you'll pay getting on £3200 in interest over 3 years). You are only employed by Channel Express/Jet2 once your licence is endorsed with the 737 so up to that point your on your own. You are not paid during training and if you're unfortunate enough not to pass the course they have no obligation to you.
Once employed you are on probationary salary for 2 months and then you are paid a substantially reduced salary for 3 years. Benefits such as private medical and loss of licence apply to captains only I believe.
Jet2 require captains at the moment. To illustrate how poor this deal is, a non-type rated captain after joining earns £49334 for the probation period then £53761 for 3 years. There is no sector pay.
When you compare this to the salaries and packages offered elsewhere in the "lo-cost" sector it would appear a no-brainer unless you're desperate (especially if you're a captain).