So in all that the answer to my question seems to be....... strike a balance that makes you feel confident in your vehicle between the BMW recommended maintenance and mike miller's and ofcourse your wallet. What i'll probably do is be proactive on replacing cheaper parts according to Mike's plan and mix in elements of BMW's. For example i will replace T-stat and Wpump at 100K as this is their appox lifespan anyway but not the entire radiator and hoses if it is not leaking and unless i have a problem i probably wont change the tranny fluid either unless there is an acute problem. However oil changes are pretty cheap and as a crucial fluid i think that its good insurance to change this as per mike's plan - i will prob do it every 7,500 miles (mobil 1). pads/rotors i can leave to idrive to tell me since i beleive that system is pretty conservative with these items anyway.
I guess we all have to rememeber that the cost of parts is not an indication of how long they will last. Waiting for the day the radiator blows is understandable for cash flow reasons where as replacing chaper parts that are known to fail around certain timeframes before they have actually broken is also an understndable plan if you want to increase the reliability of your car without costing the earth.