You can't 'officially' buy a multi-region DVD. For the reasons, see here (but note that the link to a recommended player is now out of date):
http://www.theanswerbank.co.uk/Technology/Ques tion311653.html
You have to buy a region-coded player and then hack it. (It's easy to do. Normally you just have to do something like pressing a 4-digit code on the remote control, while the DVD drawer is open).
Even though dealers aren't meant to sell you multi-region DVD players, there's nothing to stop them providing you with the appropriate hack when you make your purchase. That's exactly what Richer Sounds do. They've got shops across most of the country or you can buy online. Their cheapest 'multi-region' player is currently priced at �29.95 but, if you want a well-known make, they've got a Sony model for �39.95:
http://www.richersounds.co.uk/productlist.php? cda=productlist&sgroup=FULLSIZEDVDPLAYERS
Chris