Young children in cinemas.

[machew]

I thought that film was a 15 or something so a young kid shouldn't be in there

Nope a 12A, no children under 12 unless with an adult

 

[EltonFrog]

People should take personal responsibility for their offspring.

 

[Piemaster]

With a little irony, for those complaining about mobiles in cinemas (and I wholeheartedly agree). Those with an Orange mobile phone can get 2 for 1 entry on Wednesdays. It can be enough of a saving to make it worthwhile having a Orange pay as you go SIM in an old phone.
Downside is that it does tend to be a bit busy on Wednesday afternoons.