Thanks for the response, David.
To be honest 4 pin XLRs are very reasonable here in the UK, so that's not an issue. Obviously 3s and 5s are more commonly available, but I know where I can buy 4s mail order or online.
For clarity, I should have included a photo of the Essence electronics, so here it is (probably just a little bit simpler than a Series II !!!)
popjpeg{30825,Essence electrics}
popjpeg{30826,Close up of jack}
To aid you in navigation, the top control is Pan, Volume to the left and Filter with a Q switch attached at the bottom. As you can see from the jack there are 3 wires (red, black & purple) going to the volume control and then red and black to the battery. The problem is, I havent seen a jack socket like this one before and I use a mono jack plug.
Hope this helps to clarify things a bi.
Cheers
Rob