I think (but not 100% sure) that the BM54 is the UK/Euro module and the BM53 is the US/Aisa module, the US/Asia module has less radio frequencies than the UK/Euro module and I think that the UK/Euro module also has half step frequencies (eg 88.50, 88.35 etc...).

I could be wrong though.

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Sept 03, M3, Silver Grey. Retro-fits: Modded Mk4 DVD Drive, OEM Bluetooth, VR Control, Rainbow Speaker Upgrade, Sony SOT Amp, HK Sub, CCFL, Intravee II, NightMode.