Oops, you're correct, G; the top half is dual folding. And that's enough for me to abandon the DIY attempt, since I'm not sure I wouldn't have to fart about with the electrics and cabling. It's possible the parts won't match anyway, since I know from other F&S users at my club, whose trolleys don't match mine even though they come from the same manufacturer.
Thanks for your help, but blacksmith it is. Now ... where's that Yellow Pages gone? Ah, here's an online version.