)No obvious cause for the fault after initial investigation, and was beginning to look if I might need an auto electrician. Which was a bit galling as I served an apprenticeship in electrical enginering!
Hey Ho! Car electrical systems these days are more complex than they were in the early 60's!! Started a search on the forum with no joy but on trawling the 'Techie section' eventually found a reference to a similar fault which suggested that a line fuse had blown and this was situated strapped to the fuse box on the left of the main battery.
With hope in heart leapt to wrestle with the recalcitrant Bongo.But felt like John Cleese opening up the lid of the 'Bombe Supreme' when no such fuse emerged.
Then reasoned that a fuse could be at issue and started a search of all the fuses. Eventually reached fuse which controlled the interior light (10 Amp No 1 in the drivers knee area fusebox) which by sods law was the 25th fuse I checked!!
) Bridged this with a fuse wire and 'voila' we were back in business Quick trip to Halfords to obtain a mini- blade fuse Plus some spares!!
and the job was boxed up. 
Total cost of repair? About 30 pence.
Total cost on face saving? Immeasurable I was amazed that one blown fuse could cause such havoc with the electrics and thought that this info might might be useful for others use?
Once again the Bongo Forum has proved it's worth, The wiring diagrams, fuse codings and forum tips helped save the day. Thanks to all involved
