Polystyrene, what is a good glue?

Hi folks,
I wish to make some boxes from 20mm sheet polystyrene, but not sure of a glue to join up corner butt joints?
Thanks

Pva

I've been using a cheapish PVA from Mitre 10 (as opposed to my Titebond) to glue some polystyrene to plywood for my sons train layout. It works pretty well, try it on some test pieces first.

Try silicon ie "Selleys roof and gutter". But be aware it can have an instant grab effect.

Thanks China I will try it.

Thanks pva is a reasonably priced glue as well