Many thanks to those who put me on the track of dabonwheels.co.uk. I ordered an SMB female to FME male adaptor lead from them, but unfortunately today they wrote back (very courteously) to explain that they have no stock. So, Question One, does anyone know of an alternative supplier?
Today I investigated the van's connections to the radio. There is no way of knowing (by looking) what each cable does. They are all colour coded of course but I can't find any info about which colour means what. I'd be grateful if anyone can help. The van is a 2009 Transit 350. (It's only done 37,000 miles and it's in brilliant condition. Now I'm on my own I can't see the point of having a van and a car. I could do without the car but not the van, so that's why I'm putting a better radio in it.)