(The one by the oil filter - not by the gearstick).
Seems that these are still NLA new, so I have just recieved a new replacement used on Land rovers that may work from Old School Minis.
It looks right - just the spade terminals seem different...
according to other related posts I may need to shim it and/or file the plunger to get it working correctly.
Must say its the first part I have been unable to get "off the shelf"
Will let you know how I get on.
Matt