Ok have managed to get it running
The original notes that the seller gave were indeed correct - despite
there being a missing wire on one of the pins and the different colour
scheme on the wiring..(I know it doesn't matter what colour the
insulation is on the outside -I was just paranoid that I couldn't really
afford to burn the mysterious black box full of voodoo out)
Got a confirmation email from the seller that the pinouts are indeed
correct and to try it out

So just to clear it up for anyone else in the future..

If you have a ZKE IV module - the lock / unlock pins are in the yellow
26 way connector (central one) on the module
The connector is easy to dismantle and re assemble (and is self
explanatory when you look at it)

Unlock is pin 4
Lock is pin 17

I ended up just baring a piece of wire and pushing it into the hole
(unlock pin 17) in the connector and curling it round the end - which
seems to make good connection and hold the wire in place OK

Indeed Dave you are quite right - it just momentarily puts a 12v to the
pins mentioned above (via internal relays - nothing fancy - hence the
price :-)

The unit I got was really cheap (eBay)
It also rolls the windows up by using another relay and a third output
from the unit (by holding it in the locked position for a few seconds)
a bonus to this is if I hit the unlock shortly after hitting lock -it
dead locks the doors and locks the petrol flap :-)
I know that you can do the same thing by using a pair of diodes to
automatically dead lock , but am happy for now that hitting lock unlock
does everything I want it to
The only downside to this is you have to wait till all the relays have
stopped doing their stuff (30 seconds I suppose?) before being able to
unlock the car from the remote - not that this is a very likely scenario

Regards
Rob