I am sure that the 20kg allowance on hold luggage dosn't apply till November departure dates, up until then its 18kgs.
Davey, this is my grudge too with Jet2 they never carry enough inflight food, sandwiches (Especially on the return journey) and cabin staff always make an excuse when you complain. I now buy a sandwich in the airport just to be sure of having a bite to eat on the journey. I know their planes are getting a bit old but to me as long as you get from A to B safely on a relatively short flight thats all that matters, with a turn around of of 30/45 minutes i dont think they have time for cleaners to board the plane and clean, they expect previous travelling passengers to keep it tidy, or clean up their own rubbish. End of the day you get what you pay for, other carriers can be a lot more expensive, depends when you book and whats on offer on the web on that certain day.
All in all I think Jet2 are ok but they are upping their prices with adding extras on for hold baggage (But all airlines seem to be). When they first started charging for this is was £3 per flight leg, then £4 and now £5, even Monarchs hold charges are only £3.98 per flight leg, Easyjet is only £2 per flight leg, Thomsonfly £5 per flight leg. All extras which add onto the finances of your holiday. Cheers Jayjan