Oh ... forgot to mention in my earlier post. I bought a couple of handfuls of 1-Wire temperature sensors and hooked them up using a BUS wiring structure, and used them to monitor temperatures up and down the thermal stores, and at various flow & return points on pipes. Found them invaluable in the early stages (and cheap), locating things like within-one-pipe thermal siphoning, valves coming on in the middle of the night for no good reason, and so on. They've gone into retirement at the moment (a bit too "boy's own" for longer term usage), but I could really do with a new, better, system that allows monitoring of lots of temperature points (around the house and greenhouse, let alone around the boiler) so I'm on the lookout for something suitable, and cheap-ish.
I use the Vesta system for monitoring and control... I dont know what cheap is to you
after checking all those pics of your expensive system.. check it out
http://96.54.66.117/public/huff.html