In the parts book I found the heater hidden away in the 'Special Accessories' section near the back - it took me a while to find it I still find it strange that a heater was an optional accessory - I can understand that in 1910 but 1950 - that's just doesn't make sense.
My '46 Minx has been fitted with a Smiths heater - this required drilling of radiator pipes and soldering on brass fittings and also drilling a couple of holes in the bulkhead for the water pipes. To turn the heater on or off you have to open the bonnet and turn the brass tap. A heater isn't even listed as an option in the factory parts book - I suppose you were expected to wear a coat, hat and gloves whilst driving!
I don't know what the thread rate is - but I did note that the oil sump plug is BSP so they obviously did use it. I do have thread gauge (somewhere) but I can only check the fastback temperature sender - this might not be the same as the series car.
Hi all, I've finally sorted the problem I have obtained a T piece with BSP threads to fit in place of the temp. sender with a male, into the remaining female ends I have fitted the temp.sender and the heater hose fitting. It is in brass but a coat of Hammerite silver paint has made an acceptable modification. Thanks for all the input. Regards John