If it has the iDrive then try this

Switch on the ign - don't start engine - press the mileage trip button until the
" ! " shows on the dash the press it again - the service reset will show in the
speedo display. scroll down till you find the one you need and reset.

if you get it wrong don't worry. switch of the ign wait 20 seconds and start
again

I have a 325Cic and you're right, it's a combination of things to reset the
display (from Bavarian Auto)

You can reset the SI (Service Interval) indicator yourself
using your BMW's key and the trip odometer button. This procedure applies
to all 3 series 6/00 thru 05 and 5 series 6/00 thru 03.
1. With key in OFF position, press and hold odometer reset button. Turn
the key to the ACCESSORY position.
2. Keep button depressed for about 5 seconds, until either of the following
appear in the display: OIL SERVICE or INSPECTION, with RESET or Re.
3. Press the button again and hold until RESET or Re flashes.
4. (5 series only) Service due is shown with RESET if the measured
consumption limit has been reached and resetting is possible. If RESET
is not shown, the minimum limit has not been reached and resetting is
not possible at this time.
5. While display is flashing, press button briefly to reset the SI
indicator.
6. After display has shown the new interval, the following will appear in
the display for approximately 2 seconds: END SIA.
NOTE: The SI can only be reset after the vehicle has been driven 50 to 75
miles (consumes at least 2.5 gallons of fuel). As noted above, if the
display
does not show RESET when attempting to do a reset, then the minimum
driving distance has been fulfilled and the system can be reset. You should
also know that changing the position of the key while performing an SI
reset will abort the procedure.

I have it now - thanks to all.

Ed