I tried again this morning and still got an error message, but I've just given it another go and the order has finally gone through ok. Hopefully the issue is fixed for everyone!
Got '+' for my daughter, can't seem to get the shirt online, Beth is being very helpful. Edit: I'm not a '+' myself.
I ordered mine but specified that I wanted to collect them. Does anyone know if that means I just need to go into the shop with my confirmation, or wait for some further correspondence telling me to do so?