A few years ago i owned a range rover l322 with a sh8gged heater control unit. Main dealer wanted £300 for a genuine rover part. Knowing bmw supplied the engine, identical to the one in an x5, i trotted down to my local bimma dealer , friendly parts guy showd me the parts exploded diagram of the cooling system of the x5 and we successfully identified the part i required.
Bmw and rover part number were different but i took the punt at only £150 and ordered the part. It turned up 2 days later, gave it to my spanner man who confirmed it was exactly what we needed.
We were both stunned that i managed to save 50% with a bit of running about and a couple of phonecalls !
my point being..start with a logical suspicion the part may be interchangable, get hold of the parts diagram for more certainty , get down to the dealer and order it . Worse case if its no go , you refund it and maybe lose 5% to 10% handling fee . Oh and it was bosch that made the part for land rover and bmw !