all members of staff who have been of help must be tipped: the butler, the chauffeur, if he meets or takes you to the station; the bedroom servants, and the cook.
Tips for bedroom servants may be left in the bedroom, but it is courteous to tip as many people in person as is possible, thanking them at the same time for their assistance. To do this, you may have to find your way to the kitchen or garage, but it is worth the effort as a marked courtesy.
If you are uncertain about how much to leave, ask Her Grace for advice rather than take the chance of leaving either far too little or too much. If you get it wrong, you will not be invited again.
Seems some folk believe the "machinery" is for real, constructed out of farm machinery components in the Engineering School of the University of Iowa. Don't believe everything that reaches you by email!