Well, all this messing about has rekindled my enthusiasm for 6502's, and with further searching I've found various modern SBC designs, so ordered a couple of different PCB's to play with
Microsoft long ago released the source code for Microsoft BASIC, and a guy called Ben Eater has a series of YouTube videos about making a 6502 system using the WOZMON monitor from the Apple 1, and then adding Microsoft BASIC to it. Rather helpfully, he documents his experience in doing so, and how to configure Microsoft BASIC for different systems (the source code comes with nine original options).
I've received one lot of boards, and while I'm waiting for the rest of the components (and the other boards), I've been looking at a website about my original Microtan 65 - and specifically, looking at the cassette saving/loading system. So I've been playing with a PIC, and written code to output a compatible file, next I'm going to write code to read such a file - for now I'm just going to use wires PIC to PIC, no point in actually going to a tape, and apparently the modern technique is to use Audacity on a PC anyway
Do I need a 6502 SBC (or two)? - NO.
Am I going to do anything useful with them? - NO.
Am I going to build them? - YES.
Considering a mid-priced PIC can absolutely wipe the floor with a 6502, and requires no extra parts other than the PIC, it's fairly pointless - but it will be fun to do - and it's a 70th Birthday present to myself, today