Does nayone have the OEM part number ?
I did find a spanner in the end 7/32"
Picked our van up from storage last weekend and found the fan was only working on setting 4 (so resistor had gone) after a few days away I went into the dealers (Cordwallis in Maidenhead) and they fixed it on the spot 20min job and they checked the cam belt mine was OK no replacement required. This is the second time the resistor has gone though the service guy said that was unusual. Good service from them I thought.
Currently on the third blower resistor pack in less than 40K