In reply to m0unt41n:
I've got green superfeet in them at the moment. I was actually wondering if they were causing the problem tbh. I need to have a proper look and see if my toes are at the widest part of the toe box, or if the innersole has raised/lowered the front of my foot to a less wide part of the toe box.
Good idea about stretching, but they're fairly worn out as it is.
Ronan, thanks for the suggestion, I'll add it to the list.