This, plus if you're stuck in a stairwell and can't go forward or back, you really just have to stand there and wait because if anyone starts to try and move you risk others trying to do the same and then you've the very real possibility of a crush or people falling down the stairs. Terrifying.
Hopefully all the passengers were put on the next plane (although that would be likely difficult as almost all Jet2 planes are virtually full and it would be pointless travelling if people were only going for a weekend break) but if it was me I'd be applying for my denied boarding compensation due to airline fuck up.
I also avoid Manchester if I can get what I want from Leeds, which is closer or Liverpool which isn't that much further than Manchester and much quicker to travel through.