I think I got my Wii, Gamecube, PlayStation, Mega Drive and SNES off eBay.
A friend bought my DS is Japan.
I got my N64 and GBA from Cex.
I bought my Game Boy Color from an advert in the back of some games magazine.
I got my original Game Boy from Argos I think and my Game Boy Pocket came free when I opened a bank account.
I buy all my new games from whichever the cheapest online store is for that game and all my used games from eBay, Cex, Cash Converters, etc.