Hi, I have a Sarno Black Box for sale (European 230V AC wiring, with German "Schuko" plug but easily swapped out for UK plug).
Serial number 0426. Leg clamp added by me. Perfect working order. For those of you who are on the bb forum, here's a thread documenting what I did:
https://bb.steelguitarforum.com/viewtopic.php?t=314388Electronics perfectly clean. Minor modification / improvement made to prevent the Vari-Z pot from breaking (see photo). I also posted a story about the replacement here:
https://bb.steelguitarforum.com/viewtopic.php?t=316017200 € including shipping within the EU.
If you're interested, talk to me, send me your email address and I'll send photos.
Cheers!