Hi Simon,
I had the same dilemma and tried various suppliers and spoke to other restorers who had done vehicles in that colour. I had only found minute chips on the vehicle not enough for a match, but a good few years back was given some pannier frames from an Enfield that an old boy bought after the war, I sold them on, at the time not thinking about the paint sample but in my mind I knew what looked right. I bought a tin of "Service Brown " from Frank, but it was more of a green. Then a breakthrough, I was dismantling a 1942 armoured car and a large support bracket inside that possibly had not seen the light of day since it was built, had SCC No2 Brown, it had been covered so not faded. RR Services sent it to one of the major paint manufacturers and got a match, they have the spec with my name against it. If you are going to W&P I will try and remember to take a sample with me, but no promises as I am apt to forget, too many things to think of. Where are you located?
regards, Richard