Well today I went out and I came home with a Dean Markley Overlord tube pedal; it sounded pretty decent in the shop, so I'll be trying it out in my board.
It's got an ECC83 valve in it.
It neatly sidesteps the power supply question by having a captive mains lead - yep, a wire with a UK 13A plug on the end!
There was something on ebay on the weekend marked as collection only, so I sent them a message saying I’d do BIN if they’d post; they replied yes and added post, but someone got in ahead of me and nabbed it!
Many years ago I had the idea of adding an extra fret at the very end of the fingerboard, maybe a raised plate screwing onto the end face; I never did it, though.