I fly with Jet2 a few times a year, and they actually sent me a questionaire about what I thought of a 'premium' upgrade a few months ago.
From what I remember, they were proposing £35 per person per sector for:
*Priority Check-In
*Fast track security
*VIP Lounge
*Free newspaper
*Free meal-deal
*Seats at front of the cabin
I told them I wouldn't be interested... but it looks like they've had a play around with the idea anyway.
On the feed-back form I suggested throwing in leg-room would be more a pull than a free paper! Also, come on... seats at the 'front' are hardly a plus are they? You can get them for nothing at check-in!