Hands up - who's been there then - I know I certainly was getting towards that sentiment with my low brake fluid warning light fiasco.
Mrs Fergie is elsewhere in the house so I can confess to you chaps, that it was the wrong end of nearly £700. I try not to think about it.
If I may suggest, perhaps there is a friendly member near you with an identical vehicle that you can put side by side and systematically try parts out from the donor one at a time - so alternator, fuse box, switchgear etc.
Have you checked all of the under bonnet earths and the earth near the BeCM. There is an excellent site on the interweb that has all this information as to where the earth points are.
So many electrical problems are down to poor earths and our '38s aren't young anymore.