I think this is a region code problem: US is Region 1, and the UK is Region 2
To deal with this, you may need a software solution such as AnyDvd and CloneDvd2 from http://www.slysoft.com/en/ (free trial is possible), or DvdShrink from http://www.dvdshrink.org/
The alternative is to search for hacks for your particular DVD player. Many manufacturers have openly provided this information as there have neen serious questions raised about misuse of coding by distribution companies.
Read more here http://en.wikipedia.org/wiki/DVD_region_code