if you send the fax to a neighbouring force's fax #, you get a phone call from a stroppy jobsworth Plod who is not at all interested in knowing why the right fax # did not work (e.g. no paper in the machine).
If you're lucky!
A few years ago, I did just that by accident (sent it to the wrong police force). It was trip that I'd planed for some time, so the GAR was submitted way in advance (2 weeks). I sent it to South Wales police force instead of North Wales PF.
I didn't get a stropy jobsworth Plod calling me. Instead I got met by two very stropy North Wales Police Force plod's wondering why I never sent a GAR to them.
I didn't realise my error until a number of weeks later when I got home and checked my records.