So Dell have agreed to replace the dead 2405FPW under warranty. It took three goes: the first time I didn't have the serial 'number' to hand. The second time, I did have it, except it was 21 characters, not the 20 characters they expected. Third time, having closely examined the barcode on the back of the monitor, I came to the conclusion that the 21st characters was probably a check characters for the barcode, since the code wasn't centred under the bars, and stripped it off.
So, a replacement is on its way, arriving Monday. Naturally, the 2405 is long obsolete - when bellinghwoman's one blew up (identical failure mode - PSU dying with a flash and a bang on the current surge when turning the screen on) a month or so ago, she got a gorgeous 2407FPW-HC as the replacement. But the 2407 is no longer available on Dell's site.
My guess is I'll get one anyway (if I were Dell, I'd keep some spare for warranty replacements), but there's a possibility that the anticipated 2408 (not yet officially released) will actually arrive.
Oh, and Dell have apparently sorted out their couriers, so the old one will be taken away at the same time.