Bench Power Supply
At the heart of this supply is the transformer out of the PSU for an Apple computer printer. This was rated at 12V at over an amp so was fine for this job.
Besides that it contains two LM317s. One of these limits the maximum output current to roughly 25mA, 50mA, 100mA, 250mA, 500mA or 1A. The other one sets the voltage.
I also fitted a combined amp and volt meter which I got off AliExpress, there's no point supplying a link as such things change so quickly.
A PDF of the circuit diagram may be found here.