Whippendell Wood in Watford (just north of London) was used in Star Wars Episode I: The Phantom Menace.
I went there on December 23rd 2010 when it was covered in snow so it looks more like Hoth than Naboo. Not quite as much detail as other Whippendell entries on this site but interesting to see the shots in the snow. You can see the article here:
I'd like to thank the people on this site who have been there before and made it a bit easier to line up some of the screenshots.