Because Rimmers are having a sale on some stag parts so to balance the cosmos other prices must be higher. That said sometimes the odd thing is remarkably cheap, never the thing you want though.
Because the item from Rimmers, as supplied by Rover, is the pump and all the other bits and pieces. The MKON is just the pump meaning you have to extract the old pump from the total gubbins and then fit the pump to the rest of the gubbins.
Pumps replaced, and some idiot of a BMW driver got so close to my rear bumper put my foot down and he became asmall image in my rear view mirror.....car now back to normal.
An alternative is an ITP element from a 306 HDi. Our black one has one fitted as it matches all the specs of the orignal pump. You have to do some dissassembly and swapping bits about, but total cost is about 50 quid.