pal beatmania is its own mix I think. It was beatmania for people who lived in the U.K., and this mix will NOT work a U.S. PSX/PS2 or a japanese one(s).
the game is not very rare actualy, you can find one for a few dollars on ebay everytime there is one on ebay, and the game is just plain shit.
The japanese mixes are fantastic however.
Also if you are going to get a japanese PS2, deffinitly get beatmania IIDX (go for DistorteD, its the newest game). Of course you can buy a japanese DJ controller, or you can get the U.S. bundle for $20 (supposing you live in the U.S.).
Many people shop at playasia, which is the first place you should shop foir anything just because no one really has any problems with them, and they take most types of payment, including paypal.
here is the link to the website...
Buy Video Games for Consoles and PC - From Japan, Korea and other Regions! - Play-Asia.com
of course you could also mod your PS2, but it will Void your warranty, anf there is a chance you will break your video game console if you dont know what you are doing almost 100% of the time (I broke mine, so i bought a japanese PS2).
ya... hoped I helped.