If you don't have the good fortune of having working old-school kit to play with, there's always FUZE BASIC on the Pi:
Check out their "Special Edition" cases in BBC Micro colour scheme:
They also did a version that used the Colour Maximite PIC32 board instead of a PI, with a minimal OS and BASIC for faster boot time. The Maximite also had additional Arduino-compatible I/O.
Buying one of the cases or kits is more like an 80's computing experience - you even get wire-bound manuals in the box, none of this "documentation on CD" nonsense.
You can put the more advanced kits together a little more cheaply by purchasing a Pi separately, and Maplin have the USB robot arm from the Model R kits on special offer right now - A37JN at £29.99.
I cut my teeth on the ZX81 and Spectrum, moving from BASIC to Z80 assembler, and on to Forth (anyone else remeber White Lightning/Machine Lightning ?). After getting a +3, I bought CP/M, Locomotive Basic and HiSoft C. Then I was away to Uni, and tinkering with VAX/VMS and Ultrix-32.