Hi John & Ian. Thanks for your replies - John for the Rudge diagram and Ian for some encouragement to persevere with the 3 brush setup (likewise, I will never be out on the roads at night!).
Looking at the Rudge diagram I noticed that the resistor was bridging terms 2 and 4. Looking at the inside of my Miller I see there is a bridge (photo on my post a couple of days ago shows this) so I have suddenly (and belatedly) realised this could be a resistance - even though it just looks like a copper/brass connector, So I dismantled it and checked with the multimeter and low and behold it came up with 8 ohms!
The puzzle now is why is there a second resistor (also measured at 8 ohms) between 3&6?
I'm so sorry to have misled you chaps by saying there was no resistance - anyway, I guess this is good news.