First, I went for a HERMS because I wanted to recirculate the wort and help maintain a constant temperature without running the risk of overheating the wort. HERMS is different from a RIMS in that the wort isn't directly heated (by an element e.g) but is instead warmed up as it passes through a controlled environment on its way back to the mash tun.
This is what I bought:
A length of half inch pipe
A 10m tube of beer pipe (3/8's I think)
a solar pump from HK
a tattoo gun power supply with foot switch
some hose pipe connections and
a Lidl jam maker (already had this actually)
Once connected and running, this is what it looked like...

Ignore the mag pump, that was for the serious shifting. The set up was from mash tun via half inch pipe into the solar pump. From the pump into the beer pipe which was coiled around the inside of the jam maker which itself had hot water in it held at about 78C. The wort pumped through the beer pipe, heated up a bit and fell back into the MT continuously recirculating it. After a bit of tweaking and insulating the exposed pipes with pillows, I managed to work out the optimum settings and got the wort to stay at exactly 67.5 for over an hour and the wort ran crystal clear. (I did recirc a few jugs first before switching the pump on to avoid heavy muck getting dragged through).
Other views...


I soon realised that the foot switch was really helpful to adjust the flow speed by trying different voltages, but when I had the right settings, I had to put a weight on it to keep the power on. I've got to say it all worked a treat and without any noise too. No idea if it's made a material impact on the beer quality but I definitely got a better efficiency than planned (got about 85% compared to 80 planned) and the wort was definitely clearer than I've ever had before. Plus I never lost any mash temp at all.

Later I tried to use the set up as a chiller with the jam maker full of water being fed by the hose and the tap open releasing the warmed water. It worked really well at getting the temp down to abut 80 in about 10 minutes (120l volume) and made the boiled wort run extremely clear, but it would have been too slow for a full chill down. Colder water and more pipe might make a difference but I'll stick to my plate chiller I reckon.
All in all, a really simple set up and so far really good results.