In my 1999 / 2000 4/4 Zetec it was nearside behind the dash.
However its fitted inside a tray that's held by 4 special security screws from on top of the bulkhead inside the engine bay near the windscreen wiper motor and expansion tank. So you have to unscrew and lower the tray inside under the dash.
In theory the screws go into captive nuts underneath but mine weren't very captive and kept spinning so I had to get my head into the footwell and hold the nuts while my wife undid the screws from the top. Also the nut wasn't really a nut but a strange circular thing that was very tricky to grab hold of.
Good luck.
