Doubtful, it's entirely at the Dealer's remit. You have up to 14 days if it was sold online/via the phone under distance selling regulations - but unless the mats are damaged on opening, you're not entitled to anything under the sales of goods & services act because you don't like the quality.

And yes, that sucks.

On the other hand, this idiot on eBay thinks a set of M3 mats are worth £1200!
http://www.ebay.co.uk/itm/BMW-E46-M3...oAAOSwB4NWueRm