When I investigated the Holy Spiritual Text (aka Haynes Manual) in the wiring diagrams, I could not find a place for a bulb behind the Altar (temperature gauge display). I came to the conclusion that it was going to be more of an Eccumenical matter (perhaps a loose connection, rather than a bulb).
But, either way, the dash top was going to have to come off (maybe the steering column shroud too - see Holy Text) so that I could have a look.
But then it re-illuminated itself and hasnt given me another un-Enlightened moment since.
Praise the Lord for that!