GentleGiant

Thanks for that.
 
I picked up a new switch for £8 from my local motor factors as he was right next to the scrap yard, it has the spade terminals, so I fitted some crimp connectors and got it working. With the fresh anti-freeze it took some work to get the engine hot enough for the fan to cut in!!!
Even after a couple of vigorous 10 mile runs, I still had to sit with the engine revs at about 3,000 rpm for 5 minutes to get the water hot enough for it to cut in!!!
 
I found another obscenely overtightened bolt though, the coolant drain; even with the largest extension bar I could find, I couldnt get the thing to undo, it was starting to round off!! So I had to settle for undoing the lower hose and flushing/refilling the radiator and expansion tank only - 4 litres instead of the full 6 litres. Luckily it appears there was NO anti freeze of any type in the old water - just rust and possibly "Radweld", so I didnt have to worry about mixing anti-freeze types. (I checked it with a tester before starting).
 
I used the pink stuff, it is only a 1/3rd mix; but hey, I can only remember it getting down to -18c once in the last 30 years around here. The tester says it should be good down to -25c anyway.
 
I need to work on my hand muscles, I used to be able to crimp hundreds of 1.5mm cables every day with no effort, but I needed two hands to close the crimpers on those spades!!!!