Unfortunately having had the new layout fabricated I carried out some further checks on the layout which revealed a couple of errors that, whilst not rendering the boards completely unusable, will require changes to the firmware that I had hoped to employ. The errors are being corrected for the follow up PCBs that, once finally proved are to be professionally assembled. My 'hotplate' endeavours, whilst good enough for prototype testing do not satisfy my aims of consistent quality and a repeatable product.

The Gerber files will eventually be available on Github but to give a 'taster' of the design I am attaching two images, courtesy of a 3rd party Gerber Viewer. Highly recommended as a check that your chosen fabricator has got a correct interpretation of the files. I've only shown two views but all layers can be viewed individually or collectively.