The 1980 switch KTP9003 (Midland Sports & Classic) (seal KTP9005 not shown) retained by ...
... clip KTP9006 (Midland Sports & Classic). Both these switches have two terminals as they switch 12v to the fan(s).
The radiator header tank was modified to take the later switch so is unlikely to fit the earlier radiator. John Pinna showed how top hose clamp positioning can hold it in. However it could be pressing on the wires and damage the insulation, it might be an idea to position some kind of buffer.
V8 'Otter' Cooling Fan Switch
The switch uses a bi-metal strip to 'ping' a contact open and shut to get a clean electrical make and break.
The contact resting on its back-stop with clearance to the internal part of the spade connection. When I opened up mine it was pinging back and fore OK but not always making a good contact, even the low current of the relay is enough to cause some arcing at the contacts due to the relay inductance and back-emf. I tried cleaning the contact surfaces, but there is very little room, and by the time I had finished it was no longer pinging back and fore. I'd already bought and fitted the Burlen replacement by this time, this exercise was just out of interest.