Don't know the finer points, but there have been discussions previously on Mudcat including people in the USA wanting to play UK discs. Try a search.
The main warning I recall is that DVD-Drives on computers will change between Regions only a handful of times but once that small number of changes have been used, it will only play whatever was the final change.
I recall someone in the USA keeping one computer for playing UK discs and a second for USA ones.
Main advice for playing is use a multi region DVD player not a computer.
Quack!
Geoff the Duck.