Solution found! There was a very slight air leak between the air intake grille (four feet up the van body behind the driver's door, marvellous for driving through really deep puddles, or trips down South..) and the surrounding bodywork, the pipework must have been acting like the horn on a mechanical phonograph. Removing the gasket that joins steel bodywork to flexible pipework, adding a thin bead of bathroom silicon, then refitting has brought about virtual silence in the cab, but naturally, this improvement to my driving conditions has also highlighted at least a dozen other noises that I simply hadn't noticed earlier. Imagine; a steel / GRP composite body that creaks as it's being driven

, I thought I'd left that sort of thing behind when I excavated every single kilo of Cataloy from my old FE series Vauxhall VX1800 and replaced the plop with fresh steel.
I still plan to fit a decent wireless set to the van though. It has only slightly less interior volume than the mobile cinema which serves these here parts (when its ownership committee can afford some insurance) and that means that some stupidly large old speakers and a massive, understressed a/f amplifier can also be fitted without compromising sleeping or cooking space. I'll show the Barry Boys crowd what loud music is!
