Here in the UK we get the worst PSN store, we get everything later and the Americans get more stuff and the Japanese get more stuff then the Americans.

So this is how to access the US/JP stores on your PS3, and dont worry it dosent affect your UK account.

1) Create two new user's on your PS3 through the option on the far left of the XMB.

2) Obtain a USA address and a Japanese address. They are easy to get, try looking on a corprate information page on a large companys website. E.g a rarther large search engine's information page!

3) Now log in on your PS3 with the user who will be your USA store user, and under "Network" in the XMB select "Sign up to Playstation Network".

4) Follow the steps and use the USA address you "obtained" in step 2 to complete the sign up proccess. --- NOTE --- It is a good idea to write down which box wants what information for each of the signing up steps because when you do the JP PSN store all the instructions are in Japanese and you wont know what to write in the boxes.

5) YAY! You should now be able to download from the US PSN store. Sign up to the Japanese store the same way you done the USA one but using the JP address. -- NOTE -- on the Japanese sign up process the address input page is slightly re-agranged compaired to the USA address stage, so you may need to play around a little but its not hard!

Got it from another forum and slightly edited it btw ....saved me typing it all lol i got GT5 demo from Jap store ages ago but might be on Usa now i haven't checked tbh. 

PS3 Uk tag - Throttle -------- Usa tag - ThrottleUK

games owned -FightNight 3,Forza 2,NHL 2K7,Bioshock,MOH Airborne