Rather than ask for fixes I thought I'd place a list of the faults
I've had and the fixes we eventually found.  I'd be interested to see
if anyone else has had the same issues (especialy the AFM one)

When it's going, it's a great machine, but you really need to be a
genius to chase failure symptoms to the actual fault (or have an
Autologic or Testbook).  I have made use of a very broad selection of
swearwords and a broader amount of cash getting this littany of faults
rectified.

HDC/TC and ABS lights / The Three Amigos.  I had two causes of this
about 6 months apart.
This fault was intermittant to start with. My garage kept resetting
the computer and they would stay off for a few weeks as the faults
were caused by the SLABS computer log filling up with faults relating
to power.  This was traced to the alternator putting out a slightly
lower voltage than required. The alternator eventually failed
completely so I replaced it (John Deere supply an alternator which is
identical to the Landrover one but is half the price)  This cured the
ABS/HDC/TC faults for about 6 months.

The lights returned and this time I needed to replace the ABS Valve
Body.  There is a part replacement if you can get someone keen to take
it on, otherwise see if you can part exchange your existing one.  The
price from a dealer for a new one is painful.  You can still drive the
car with the three amigos lit but you have no ABS or TC.  Bear that in
mind.

Failed Air Flow Meter - truly weird.
My Disco started running really crap at hgher speed, would go like to
clappers up to 50kph and then run out of puff.  I checked everything
that I could think of - plugs/leads etc.  Turned out that the K&N air
filter had caused the Air Flow Meter probe to malfunction.  Don't
ever, EVER put an oil impregnated air filter (such as K&N) on your
Disco II or Range Rover P38.  It will wreck the AFM eventually.  If
you've got one, get rid of it and put a paper one in.  I couldn't get
a Disco II AFM easily, but my garage managed to fit a P38 Range Rover
one as it is the same part but needs to be spliced to the wiring
harness as the connector plug is different.

Cruise Control Failed
The cruise control gave up due to the vacuum hose fracturing and
unable to hold vacuum. Easy replacement.

A real strange one
One morning my engine fired up normally and after about 5 seconds
flashed the transmission failure lights (M ans S flashing).  At the
same time the engine dropped about 400 RPM below normal idle and
sounded like it was running on 4-6 pots.  It wasn't misfiring or
smoking, but had very low power.  I sh.t it off and pulled the battery
lead off for a few minutes.  When I reconnected the battery the lights
were gone but the engine was still behaving weird.  I needed to move
the car so I put it into low range to makew the most of what little
power I had and low and behold the engine came right.  I swapped
between Low and High range a couple of times and the engine kept
running badly in high range, but ok in low.  I took it for a drive in
low range and after a couple of minutes the fault must have cleared
and she went back to running normally.  Out of curiosity I took it to
my service agent (not a dealership) and plugged it into the Autologic
box to read the faults - just a low voltage fault on the
transmission.)  Has run fine ever since.

Precision British engineering - just love it. ;-)

Chris,
Wellington, New Zealand.