Re: I *wanted* an Acorn Archimedes when I was at school...
I think the same is true for all Acorn's pre-Archimedes BBC machines, including those with 16 and 32-bit second processors.
Absolutely. While the Acorn machines had very little compatability with other 6502 devices, the fact was that in the multiple generations of machines Acorn produced, so-called "legal" programs were usually portable. Legality meant using the OS calls rather than ?-ing (PEEK & POKE to non-Acorn types) memory directly. To put it in slightly different terms, Acorn defined an API and very strongly encouraged people to use it.
The Archimedes was slightly more difficult in that it didn't natively take 6502 code (though Acorn bundled an emulator from the outset) but BBC BASIC V was 100% compatible with previous versions, as were the system calls. This did lead to some slightly odd behaviour, such as the ENVELOPE command that produced all sorts of useful effects on 6502 hardware being essentially useless on Archimedes due to the completely different sound system. Someone once said, "ENVELOPE takes fourteen parameters and does absolutely nothing."
But Acorn's efforts couldn't match the combined might of Intel and Microsoft, and in some ways it might be a good thing that they didn't as it enabled ARM (once it was spun-off) to do the clever things they have done with licencing and low-power and suchlike. If Acorn had been successful on the desktop, perhaps that wouldn't have happened?