I once got ripped off for £750 by a local furniture company (took my money twice from my debit card).
I resolved the issue by printing flyers describing my story & standing outside their entrance, giving my flyer to every person who was going to enter their store.
Within the day, my money was paid back in cash to me. They lost so much more in people reading & turning around to walk away.
Lets hope Brownhills see your story over every web forum in the Uk.
I would be renting a pitch at the next Motorhome show, getting myself a banner ("A Warning to all") and displaying your story to anyone that wants to listen.
Their credibility needs to be severely knocked over their treatment of you. Something like this, handled correctly, could be the nail in their businesses coffin. I'm sure your forum friends would help out too.