Instore in my local Asda (Middlesbrough) they had a new* display full of accessories for the DS and Wii. All items were £5 each or two for £7.
Pick of the bunch, in my opinion, was the DS Lite starter kit. Contains zip up EVA case, wrist strap, two replacement stylii, a pair of headphones, and a cleaning cloth.
They only had the kits in pink and black in my store.
Other items in the display included wii balance board silicone skins (clear or pink), glowing wii tennis racquets, wii light gun molds, and others that I can't recall.
The display was near the front of the shop, and not in the entertainment section. Almost identical kits in the entertainment section were priced up at £10 each. (There were also kits with less items in, there, for £7 each.
I'm assuming this is nationwide, as most Asda deals are, but as they appeared to be priced to clear stock may be limited.
*display was put up yesterday, according to the assistant I spoke to.