(Note to all wikipedians and Wikipedia.com readers: This is a list of famous people whose drug problems have been discussed in public. Because this could a very controversial issue, do not write in names of people who are only suspected of being addicted to drugs. Wikipedia might be liable if the names of someone who has been only suspected of is added).
... which were at the far end of the Metropolitan Line, and stretch the definition of "tube station" a little:
Waddesdon tube station[?]
Quainton Road tube ...