Edit: There appears to be some confusion on the forums so allow me to clarify the details about Play Asia and Last Window in Europe.
#1. The DS is Region Free.
This means that you can play the European version of Last Window on your American DS. This was also the same case in the past with GS1 - GS3 DS in Japan with past releases. So no worries.
#2. The United Kingdom (England) is a part of Europe. Last Window is being released in English.
... and Italian, and Spanish, and German, and French. When you first got your DS you had to select your native Language. When you insert Last Window on your DS it'll automatically select English to play with, should you have English as your default Language.
#3. Last Window is NOT getting a North American Release
Nintendo of Europe is publishing Last Window, not Nintendo of America. Additionally, the only trademarks for Last Window reside in Europe (and Japan). Nintendo of America has done nothing to indicate that they are interested in publishing Last Window. Add to it that the last CiNG title released in the states, 'Again: Eye of Providence', was not published by Nintendo but Temco, and that the last Nintendo of Europe published CiNG title 'Another Code: R', was not released in America. There is every indication that Nintendo of America has no interest in bringing Last Window state-side.
Therefore the only way you are going to be able to play the game is either through Play-Asia, or if you've got a friend in Europe willing to help you smuggle the game out. The end.
#4. The game costs as much as a Wii Game
Yes, Yes it does. But consider first that the game has to be shipped from Europe, to the Pacific where Play-Asia is headquartered, and then from there to the States, the game is literally traveling the world to get to your door. Such is the tale of import titles.
Also consider that games in general are more expensive in Europe then in America. The DS titles for instance normally cost 34 Pounds new. When you convert that to USD the game costs $52.51; That's what they pay locally! The add that Play Asia is playing chess with shipping the title, and you've actually got a decent deal.