I once had trouble buying a glass door for our oven (which I smashed while cleaning) I eventually found one online and unsure it was right I sent a disclaimer with the order. When the new door arrived it was wrong but an incorrect part number to the one I had ordered which was correct.
The company concerned would not take it back without insisting on a 50% restocking charge even though it was their fault they had shipped a wrong part.
I took the case up with trading standards who explained to me that anything you buy mail order which covers Internet purchases as are shipped by mail! All mail order items are of course purchased without seeing them so we the consumer have a right to return without charge. We are liable for return carriage but its our right to return without charge.
So you could buy from Jessops Internet site, tryout the goods and return just like the high street! but cover yourself with a disclaimer as part of sale terms.
If you dare!