First off here's what it all looks like at the moment

You can see the chiller linked to the cooling probe by two 8mm ID lines insulated in armaflex.
The probe itself enters through a modified corny lid. This isn't the one Blichmann supply with the conical (that's safe and sound) but had a leaking PRV of a wierd type so was useless for anything else.

The PRV hole has been sealed with aquarium silicone and the legs of the lid retainers have had to be shortened as the conical lid is flat unlike a corny keg.

The central position of the PRV was handy as it meant I could get the pipes close together. I drilled two 13mm holes in the lid and in those placed two 8mm-1/4"BSP male irons. 1/4"BSP backnuts were screwed tight on the back and then the two irons drilled through with an 8mm bit so that 8mm pipe will go all the way through.

On the other side of the lid are two 15" lengths of 8mm cooling probe that's joined using two 8mm solder-ring 90degree bends. The probe and 'corny' lid can (just) be removed from the conical whilst the main conical lid is on. If the probe was any longer it would foul the sides.
Does it work? Well...better than I thought. In trials using water it kept both 20L and 30L at least 10C below ambient in my overwarm garage. That's using an uninsulated conical. If I put a bit of neoprene around it I reckon I could brew lagers easily in the middle of summer.
Now some of you may have noticed that this isn't 'Temperature Controlled'...it's just uncontrolled cooling. For that you'll have to wait for the next installment.....when the stuff turns up from Maplins and I put it together.