Do you use your UK listed credit card on those sites,i thought to use a Japan store you had to have a credit card listed in that country.
Its good for you Kila and i appreciate the savings you make,but personally the way i get bored with games really quick as you well know its not something I'm to interested in because once you buy digital content there are no refunds and there is no trade in option.
Now something they should consider in the future is the option for you to trade in the digital content against other digital content to reduce the costs involved.
Now that would interest me

the fact you could free up hard drive space and get a discounted price on another game you wanted and it automatically deleted that game for the new one.