Thanks Normand. Yes it was neomilium's PPA and that would explain why I wasn't getting any recognition for apt install heekscad. A quick look at the build log shows it's only failing on a couple of things so far so maybe not so bad to fix. And 15.10 seemed to build fine.
I've not completely migrated to 16.04 yet and currently(even now) I'm running from an iso image on my HD with my userid created and lots of soft links from my HD into this test system. Persistence is via a 64GB USB3.x dongle. Impressively fast and allows me to test tools as I go. Like finding out HeeksCAD won't run yet.
I'll boot into 14.04, install the latest and see if I can figure out this CNC stuff. Thanks.
Doug