windows and central locking with a mind of their own

on a 03 octavia 1 tdi 90 auto we've got problems with both the windows and locking working at random

the windows sometimes open unexpectedly while driving and refuse to be closed again then but generally when closed they are ok .... but when open they repeatedly try to close again

the locking usaually stays locked - i can open it using the key button or the switch on the drivers door and normally as soon as i take my finger off the button they relock

the switch was swapped for one from another car with no improvement

diagnostics cleared loads of related faults but nothing changed

its been suggested that the body control module is the problem - possibly damp  ...... can anyone say wher thats located on this car so we can check?

or of course can anyone else suggest alternative ideas for whats going wrong?

thanks