OK, reporting back just so other people can find this via google later and not have to work it out for themselves… the replacement screens I found definitely work for Blofeld with a bit of fiddling. (and could be sent to the UK)
Contrast is better than it looks here (phone camera) although I think the viewing angles are not quite as good as the original, and the viewing area is maybe a little tiny bit smaller… but below link if anyone has a dead screen and access to a soldering iron!
https://www.artronic.eu/pl/c/Seria-A/152
Going to order another and try positive black on orange and see how that looks now… seems like it is designed to be positive as the lettering on patch names goes right to the edge of the display area, using the backlight as a border.
notes: the power connections for the backlight are about 5mm out, so you have to cut the pins down and wire these in. In turn this means the screen needs hot gluing down at the bottom to hold it steady as the power pins normally do that. It also looks much better at medium contrast rather than all the way up as the original did.
“Blofeld Replacement screen” just so that phrase is here.