I don't know if they ever actually supplied them, but I have a 1978 Signetics 'Bipolar and MOS microprocessors' Databook that lists the S/N3001 microprogam control unit and the S/N3002 Central Processing Element. AFAIK they are equivalent to the Intel parts. The UK availability chart on the inside cover seem to imply that the 3000-series were available from Signetics in the UK.

The same book also lists the 2901-1 4-bit bit-slice, the 8x300, the 8080, SC/MP-II and the 2650. And a number of peripheral devices.

One other 'fun' item in the book is the 3000KT8080SK. This is a kit (PCB + components) to make an 8080-compatible CPU using 3000 bit-slice. I would _love_ to see the documentation (which included schematics and microprogram listings) for this kit ;-)