If you don't mind eBaying or buying digitally, The Legend Of Zelda: A Link Between Worlds is a steal at just £19.50.
You'll get an eShop download code from ebay seller level99gamesltd (99.8% feedback from over 14000 ratings). "Code will be messaged to your eBay inbox between 10am and 4pm Monday-Saturday. We are not open Sunday. Code will also be posted upon buyers request (A4 Sheet with code clearly shown)."
I suppose you could technically describe the 3DS' latest masterpiece as a link to the past, since it's a follow-up and sequel to that ancient classic. That was made in the past. It links to... you know what, never mind.
This excellent adventure has some great puzzles, uses 3D brilliantly and has a fantastic wall-walking mechanic that enhances exploration. You can save a fair few quid with this cheap 3DS deal, but I don't know how long stock will last. Thanks to Geekboy2k for a great spot!