need to get some for my own car, might price them up in bosal and see how much their ones are, last time i got a pair of 320 ones for the same price as one from bmw. will let you know when i drop down to them.
i think the m3 ones are slightly different, more metal in them so stronger. u can get 320/325 ones on ebay for £9 or so. the m3 ones have the same part number as m5 mounts.