We now have enough for a list:
- Doctor Who and the Dalek’s http://www.imdb.com/title/tt0059126/ The first Doctor (normally William Hartnell) is disguised as Grand Moff Tarkin (Peter Cushing). Presumably he was in deep cover in the Empire just before hand.
- Daleks’ Invasion of Earth 2150 http://www.imdb.com/title/tt0060278/?ref_=tt_rec_tti Peter Cushing is at it again. The Dalek’s have this great idea for a planet-sized spaceship…
- Local Hero http://www.imdb.com/title/tt0085859/ A very young looking incarnation of the 12th Doctor (Peter Capaldi) and Wedge Antilles (Denis Lawson) discover oil in Scotland.
- Shallow Grave http://www.imdb.com/title/tt0111149/?ref_=nv_sr_2 The Doctor is still in Scotland but this time as the 9th (Christopher Ecclestone) and sharing a house with a young Obi Wan Kenobi (Ewan McGregor). They have to hide the body of the Sheriff of Nottingham.
- Attack the Block http://www.imdb.com/title/tt1478964/?ref_=fn_al_tt_1 disguised a trainee nurse, the 13th Doctor helps a rogue Stormtrooper (John Boyega) fight aliens in a South London Housing Estate. Father Christmas (Nick Frost) is growing dope.
I think that’s it – less than you would imagine given the heavy use of British actors in Star Wars.
[ETA: aside from the many examples below, I also forgot that the 7th Doctor (Sylvester McCoy) was also a wizard along with Count Dooku (Christopher Lee) in the Hobbit movies]