Where are you seeing the UEFA rules? All I see is stadiums must be all seated, can't see punishment for standingA bit more than that though, as UEFA requires the club to have supporters seated, and the local council also has that requirement.
Sanctions from UEFA, in addition to fines, can include reducing the crowd size for the next 'x' games.
So I hope standing wasn't seen to be too much by UEFA in the ManCity game.......
And :
The legislation relating to standing in football grounds derives from section 11 of the Football Spectators Act 1989: ‘The Secretary of State may, by order, direct the licensing authority to include in any licence to admit spectators to any specified premises a condition imposing requirements as respects the seating of spectators at designated football matches at the premises; and it shall be the duty of the authority to comply with the direction.’
So the ground could be closed if there is persistent standing, especially if the club is seen not to be tryimg to control it.
And standing breaches the ground regulations, alllowing the club to eject standing spectators, and indeed ban them.
So its not as simple as just 'a breach of contract relating to your purchase of a ticket. '
Edit.... Seen it,