I did mine mate,
you press and hold the trip counter reset button, switch on the ignition (remember to do the immob too so all the ignition lights come on) and hold the button in till the mileage display flashes and goes to OEL - then switch the ignition off before letting the button go. Resetting each entry (there are three) will show ---- then back to that entry name.
Pressing in the bottom clock adjust button resets the first service reminder OEL (oil) , press the trip button once, it changes to IN01, press bottom clock button again to clear (this is 7500 mile service marker) then repeat the trip button once more to get IN02, (15000 mile service) and reset with the clock button again.
press the trip button once more to get OEL on the display and switch on the ignition again. The display will change to IN00 then the miles or trip display. Your done!