Just fitted the diode. Excellent for only 9p. Thanks again for posting good instructions with pictures so even a total amateur like me can do it.
What went less well was that I stretched one leg into the cockpit so I could get eye-level with the switch in an attempt to avoid scuffing the delicate paintwork - didn't scuff the paint but did rip my trousers.
A-Plan are pretty good, they also sponsor a Land Rover forum (defender2.net) and I had my first year's insurance for the Landie through them, sadly they got beaten on the renewal but I'd definitely check their prices when renewal is due.