OK. I've assumed 540i, European model, LHD, Automatic.
Model code: P E39 tou 540i M62 ECE 19970900 L A

You would have had one of these antenna amps:
With nav/TV, 433MHz remote: 65258368879
With nav/TV, 315MHz remote: 65258368880
With nav/TV, Independent Heating, 433MHz remote: 65258368883

Looking at the same car, but a 2003 model (ie: with BM54), the antenna amp changes to:

With nav/TV, 433MHz remote: 65256906078
With nav/TV, 315MHz remote: 65256906079
With nav/TV, Independent Heating, 433MHz remote: 65206922875

The wiring diagram is unclear as to any wiring changes