OK just to check we're all on the same page, which seats do you have?
The first of those comes with red interior bits automatically. The second doesn't. So if you have the second, then go back to Fish Bros and politely point out that they're mistaken. If you have the first, a cost-price change is probably a good deal.
BTW, are you based in Swindon? If so, I'll look out for you!