Bought a graphics card back in April just a cheap 64mb nvidia. The 3d acceleration has stopped working. If i test it on dx the comp freezes. Definately my card is kapput. Anyway I have no receipt and have thrown away the box but I can show proof of purchase through switch. is it unreasonable for me to take it back was only £44
Your manufacturers warranty should be no less than 1 year from the date of sale, assuming that the item was not 'grey' or refurbished. Your contract of sale rests with the shop or store who sold you the item. Although due to the time that has expired it is not unreasnoble for them to send the card back to the manufacturer for testing, and assuming the card is faulty offer you a repair or replacement. I doubt if you would be able, or be entitled, to get your money back.
Your Switch receipt should be enough proof of purchase, providing it shows the name of the shop, time and date of purchase.