I'll list where I got all my current gen games/systems from:
Original DS - Uncle got from America on business trip, got a feeling from Best Buy
Mario 64 DS - HMV
Mario Kart DS - Amazon.co.uk
Metroid Prime Hunters - Game
Nintendogs - Gamestation (pre-owned)
NSMB - Game
Pokemon Diamond - DS
DS lite - Amazon.co.uk
Zelda PH - Game (pre-owned)
Final Fantasy III - BlockBuster (pre-owned)
Final Fantasy IV - Argos
Chrono Trigger - HMV
Advance Wars DC - HMV (pre-owned)
DSi - Amazon.co.uk
Zelda ST - Amazon.co.uk
Dragon Quest IV - Amazon.co.uk (pre-owned)
Dragon Quest V - Game (pre-owned)
Dragon Quest IX - Game
Wii/Wii Sports - Comet
Zelda TP - HMV
Wii Play - Amazon
WarioWare SM - Game (pre-owned)
Galaxy - Game
Mario Kart Wii - Game
SSB Brawl - Game
Okami - HMV
Metroid Prime 3 - Amazon.co.uk (pre-owned)
Little King's Story - Game
NSMBWii - Amazon.co.uk
Tatsunoko vs Capcom - Zavvi.co.uk
Galaxy 2 - Amazon.co.uk
Super Paper Mario - CEX (pre-owned)
PS3 - Amazon.co.uk
LBP - Game
Resident Evil 5 - HMV
Street Fighter IV - HMV
Bioshock - Game (pre-owned)
Bioshock 2 - HMV
Star Ocean TLH - BlockBuster
Valkyria Chronicles - Amazon.co.uk (pre-owned)
Final Fantasy XIII - Amazon.co.uk
