Ok, mine had this problem around a month ago. (2002 LR Focus)
Get someone to start ur car whilst you stick your head over the throttle body. Listen carefully for any vacuum leaks.
I had cleaned my throttle body, check
MAF etc etc, ended up being a vacuum pipe. Frustrating..... yes!!
Mine has just started to run rough again now, at 150K, going to book in for timing/auxilary belt change. Anyone no how much that'll roughly cost?