I have enough bits for two channels, and a big box to put them in (OK, not shiny, that would have cost £120 on its own), but I thought I'd lash together one set to see if it works.
This is the lash-up in a rather second-hand plastic box. The Auber PID controller is driving one of their SSRs, and a PT100 probe from Watch-Hill is plugged-in via a splashproof 9-pin D connector. Boy, do I need everything splashproof! Note the use of sophisticated blanking-off material to cover spare holes in the box (2" wide, sticky...)

In this side view you can see my finger holding the lid of the splashproof mains socket open. The test run was to see if the PID would auto-tune for the kettle, and whether the kettle would stay at 50C which would be my first mashing step. Not enough time to rig up the mash tun, but I have a week off coming up from the 3rd.

I'm still waiting to get the element-is-OK detector circuit working. I've built a dual-channel detector on a piece of Veroboard, but it doesn't detect anything at the moment. Something about differential voltages through an op-amp.