For now, I'm just for the french ones, I don't know if this work for the UK site.

1. Go To http://www.allocine.fr/video/haute_definition.html
2. Found The IDNUMBER of the trailer, mostly 8 numbers, for that open the link in a new window, you will have in the adress line something like (javascript:%20FenACVision(18635902,'',null,null,null,'HD')). Copy/Paste the number.
3. Open the Page: h t t p://www.allocine.fr/webtv/acvision.asp?nopub=1&cvid=IDNUMBER&player=QT&debit=HD
(example http://www.allocine.fr/webtv/acvisio...er=QT&debit=HD )
4. Go to the menu Edit --> Source, search for the ".mov" link.

This is my way, I don't know if there are easiest way, but it's a clue to start.