Suggested that are emulated using MAME.

These aren't PCs in the sense of the IBM PC and compatibles discussed in this forum. From the wiki:

The ABC range was developed by Acorn essentially as a repackaged BBC Micro, expanded to 64 KB RAM, to which was added (in some models) a second processor and extra memory to complement the Micro's 6502. The electronics and disk drives were integrated into the monitor housing, with a separate keyboard.

So use any BBC Micro emulator. If you just want to run BBC BASIC, there are ports to various platforms, including modern ones.

Never seen any examples of these, and I'm in the UK and have come across pretty much every type of Acorn/BBC.

Judging by the numbers stated in the article I would doubt if these were actually sold in any number or reached the market beyond a small few. In fact, just reading a little further it seems like none of them were produced other than the 210.

They basically sound like a Model B (more like a Master, minus the extra ram) with a 32016 second CPU. Something that you can actually put together without too much difficulty.

IIRC, there was a Pi based project to use the Pi as a second processor replacement, so it may not even need a genuine 32016 second CPU box tracking down.

Yep, here you go:

https://github.com/hoglet67/PiTubeDirect/wiki

Use a Pi to emulate/replace any of the Acorn second CPU interfaces, including the 32016. Add that to a model B and you are probably 99% of the way to one of those Acorn Business Computer models.