Fiesta exhaust - how much?

[Lois]

I've got a hole in my exhaust and dont really enjoy sounding like a chav in a diesel!!
I had a quick look under and from what I can see the hole is in the back box, but not sure on the state of the rest of the system.
What sort of price would I be looking at for just replacing the back box up to the cost of a new exhaust system if the whole thing is caput??

It's a '99 fiesta.

[Lois]

It sounds like it's got bigger recently.
Hopefully the rest of the system is still ok and it's just the back box.

[Lois]

She's at the doctors as i type

Looks like a nice place and I even got a free brew and lift home (could take a while as I'm having some other work done too). They're going to hopefully just to the back box which would be around £30, so fingers crossed!