Looks like Gameseek have the best price on this game and this Straw Hat Edition which includes:
One Piece Unlimited World Red Game
Flame Fist & Straw Hat DLC
Luffy Strong World Outfit
9 Costume Anniversary Exclusive DLC Pack
Vita (£20.94) & 3DS (£23.75) versions are well priced too but Gameseek charge £2.99 delivery on orders under £30.
A unique One Piece adventure to be enjoyed in co-op, with characters designed by Eiichiro Oda and a game-exclusive scenario!
The Straw Hat Pirates helps "Pato", a racoon with a mysterious power. They head to an island called "Forgotten Island", but when they arrived Luffy's friends are kidnapped. Is it a trap created by Pato? And who is this mysterious pirate named "The Red Count," who was waiting for them?
One Piece Unlimited World Red: Straw Hat Edition - Features
Ninja Battle Action – Tons of amazing fights and original animation
Original Story: new scenario.
Epic fights: latest episodes + famous boss battles.
Playable characters: 9 from the Straw hat crew.
New Characters: Pato and big boss "Red" designed by Eiichiro Oda.
Endless Playability: exploration of an expanding town.
Unique abilities: each character has some.
Co-Op: fishing, bug catching, battling, cooking, mining, battling, exploring…