Well its been a few days- combination of bad weather  and kids half term (naturally!). The car will not fit in my garage with any useful room around it so I'm pretty much limited to fine days when there is no-one else around and I have opportunity- this I can foresee is going to be a problem.

Anyway there has been slight progress. I realised I wont be able to check much of the motor with a gaping hole in the electrical system so sorting out the various electrical ancilliaries has moved up the priority- also if the worst comes to the worst and I have to bale on the project, then I will at least know what bits work when I sell it for parts!

Anyway I ordered a coil and a washer bottle. The washer bottle arrived- was connected- and didn't work. I traced the wiring from the column to the pump- found no fault so put it back together and hey presto it worked! This it turns out, is going to be a pattern- presumably its a multitude of bad contacts that have built up over the years. However its deeply unsatisfactory- if I find no fault I cant be certain I have fixed it and so that it wont come back again- bummer. All I can do is clean every contact I disconnect in the hope that this might be the problem! There should be some sort of grease you can coat all these bits with to stop this horrible gritty greenish or whitish corrosion from building up on bullets and spades- anyone know?*

*Thank you responder- turns out there are various forms of dielectric grease that should protect as well as lubricate the contacts- I bought a cheapo tub on Ebay and I'm now applying it to all contacts I disconnect/clean as a matter of course. Hopefully this will improve the situation as I move around the car!

Washer bottle in situ- the empty space offended me! Nice to fill it and tidy up at least one loose wire. Need more tubing!

During the process of this fix I had checked the fuse- given the dodgy nature of connections I thought I should remove check and clean them all- which I have now done (Fuse box is under drivers side of dash on right). Sadly I found no missing or blown fuses and replacing them didn't improve anything! Ah well one more job down.

Wipers

The wipers on the car had shown no life since I got the thing. Once more I started tracing the wires- but here it got complicated as I couldnt work out what was what! Turns out the power is fed by green wire to the column switch  but at the same time directly to the wiper motor (terminal 4). This was really puzzling and the motor seemed to have far more connections than it could possibly need! This again is to emerge as a common occurrence. Much thought later and a flash of the blindingly obvious- I eventually worked out that this is for the parking mechanism. Without a direct motor feed the wipers would simply freeze wherever they are when they're turned off! So this means that there are 5 wires going to the column switch from the white under-dash connector: the green is a double wire- (power into switch and also out to motor park system) and the other 4 are power distributed through the switch. My manual contained no diagram for how connections are made inside the switch so here is what I found:

Up position (off) No power output from switch but red/green connected brown/green allowing parking system. 

Down 1 Power to red/green single speed speed wipe

Down 2 Power to blue/green double speed wipe.

According to my wiring diagram the switch is connected to the wiper motor directly- but this isn't so. The switch went into a multiplug connector that attaches to a small black Lucas box 6DA under the dash and not shown on my diagram.

Lucas 6DA controller. White multiplug goes to column, black multiplug to wiper motor

A little research showed that the 6DA (or AAU 7087A) is a single flash wipe/ intermittent wiper control; a surprise as I didn't think this car had such a system. Anyway, contents of the black box are certainly beyond my tinkering although not replacing if it proves faulty.

The wiper motor on this car is located above the passenger's feet behind the dash. The underdash panel is present on this side so I removed it. I had read horrible things about access to this motor in the Excel but surprisingly in this early car it seemed OK to get at. I disconnected the multiplugs and tested to continuity to the black 6DA connector- all fine.

Wiper motor under dash above passenger's footwell. White multiplug connector comes in from lucas 6DA controller.

Carefully I applied a 12v feed directly to the red/green terminal- and hey presto-wiper motion! I tried again to the blue green and got no movement but a very hot wire- my probe wire was too thin and in danger of melting! I have ordered a Sealey PP1 probe to help me apply power to components in position more conveniently (and safely)- will let you know how it works out!
So everything put back together- and yes you guessed it, wipers now work on both speeds although they do not park. The flash wipe also operates but since the parking isn't working the wiper freezes as soon as you release the column. Wiper parking failure seems to be a fairly well known problem on these motors- if my experience is anything to go by then it may well be yet another bad connection. Happy with progress so far- put parking mechanisms on the list to sort out later.