My electronics stuff is almost completely digital stuff - although I learned about op-amps and stuff at Uni I struggle with the analogues side. Here's my old work-bench for digital:

So remove the copper pipe and use the threaded connection in the back of the head (currently blocked), to take the flow to the cabin heater, and the closed thermostat bypass back to the pump?  I'm going to have to look closer at some old engine threads and draw a schematic.  It's my own fault with the changes I've made, but I would like the engine bay to look less like a bucket of squid!

I will run one in my 4A over the winter to make sure it works for a good length of time. I'll send it to you in early spring. It is a direct swap.   Roger 

My feet do not get on with flip-flops. Some may do but mine is different.   Roger

^^^This. My Vitesse is plumbed this way.

Hello, What is the dull red forlorn looking object behind the motor?? Regards, Michael.

Hello Nick, With a lot of luck we will now have a few photo's. 1st photo is bump stop and it's mount.(at base of ruler) Shiny circular part on far right of second photo is brake drum, Dark bit at bottom of third photo is back of brake drum. Other two are underside of trailing arms. Regards, Michael.

Interesting, I thought it was done with a flip-flop circuit? 

Hello Roger                     All that above my pay scale !! But I have two of your old! boxes one fitted to Spitty(which works perfectly )  the other waiting to fitted in the Vitesse !! (plus a good friend runs one as well!) but if you want me to send it back for the Super upgrade I will and fit it to Spitty for a good testing next year(Spain booked for June and hope to talk Memsahib into a second trip later!! I am a bugger for trying new bits like you do its bit like tweaking engines because you can it's not about the power(to me it's engineering type things Spitty seems to go well and can hold her own if in the right gear at the time(but does not have the flexibility of your sixes so requires skill??Luck? foot down in lower gears then she surprises them! roger

You can use the standard housing if you're running Webers/injection as the connection for the heated manifold is redundant and therefore available for the extra sensor. Use the heater return pipe to the back of the pump housing for the Mk1 Spitfire which only has a single connection at the back of the engine. Helps keep the hose count down!