This is just not on, Jacqualina - especially as you've been a good customer of theirs.
Just a thought - have you actually spoken to Outwork about it yourself? It seems most unlikely that they won't repair it; perhaps Gems just didn't want to foot the cost of the repair! If Outwork say they can repair it, you can then use this as ammunition when you speak to Gems again.
If Outwork can repair it, and Gems don't want to play ball, I wonder if you could pay for the repair yourself and then sue Gems for the cost in the small claims court? Or have they fulfilled their legal obligations by offering you a refund?
(My father once sued a garage for £30 in the small claims court - and won! When we were clearing out his papers after he died, we found a thick file relating to the case. As I understand it, there is no need to involve lawyers and so there are no costs; but you do have to be bloody-minded like my father was!)