There is an even closer chinese supermarket in Mitcham called Hoo Hing. It's not as big as Wing Yip but handy if you can't be bothered driving to Croydon. Hoo Hing is right next door to Smyths toy store (handy!) so if you need directions take a look at the Smyths store locator website.
There's a great restaurant/take away on Bedford Hill across from the Sainsbury's carpark - Bento. They do Chinese as well as some Japanese. Huge selection of food including dimsum and big soups which you wouldn't normally get at a takeaway. Staff are really friendly girls as well.