Hi John,
welcome to the community!
May you can explain the problem more in detail?
Unfortunately you forgot to mention if you own a Series 1 or Series 2 model with 4 or 6 Cylinders, manual or automatic gearbox?
The power window relais & fuse are located at the central control unit (CCU), which is located (for LHD's) at the outer lower left side beside the pedals.
The door lock relais & the keyless unit are located at the outer right legroom. The fuse is located at the CCU.
I imagine, at a RHD all the stuff will be located at the opposite side of the car.
The buzzer should sound when:
1. ignition key is in off-position and drivers door open
2. ignition key is not in nuse and lights are on and drivers door open
3. drivers seatbelt is open and ignition is on
4. as far as I remember, if the ABS control light is defective.
So as you described, I would think about a bad ground connection.
Main relais or ECI relais are surely not not part of your discribed problem.
An excellent source for used spareparts (here in Germany) is still
www.xedos-shop.de
another source, specially for RHD's from England is
japanpart at
www.ebay.de
and, of course,
ebay uk.
so long,
John