I take it you are aware of the DVD region issue ?
You probably know this already, but just in case: DVDs from the US are region 1, disks in Europe are region 2. By default DVD players will only play one region, but many DVD players can easily be hacked to play any region.
So make sure you check ahead of time that any DVD player you buy is easily hackable (some are hackable by burning something to a CDR and playing it in the DVD, others are hackable via pressing buttons on the remote and most of the rest are hackable via a hardware hack).
Alternatively you can buy a player that has been pre-hacked from someone like
http://www.codefree.com/ (the people that I bought my DVD from years ago). You pay a premium this way, but get peace of mind because they waranty the player and their hack (hacking a player will likely invalidate the warranty).
...and what do you know, top of their front page is a player that does multi region and multi voltage...
http://www.codefree.com/dvd_codefreed8500.htm
Looking at their comparsion chart
http://www.codefree.com/dvd_comparison.htm only their own brand players do 110v and 220v.
You do pay for the privelege though, they want 299 Euro for their multi region, multi voltage player. You could buy a 40 GBP player in most supermarkets in the UK that could be hacked to multi region via a CDR, but they wouldn't be multi voltage.