Wet Steering Box (Disco II)

I bought my Disco a couple of months ago and when I picked it up they told me that they had replaced the drag link and sure enough underneath there is a new (LR sticker shines) link.
I noticed and my neighbour noticed a little leak on the ground, on looking below the the drop link from the steering box was wet and had a little drip on it. I touched it and the fluid seemed like WD40 (smell, colour, etc.) so I assumed that they had soaked the drop link in WD40 to help let the drop link be removed.
The patch on the driveway has got bigger and bigger so I know now I have a leak!!! I looked under the bonnet and in the PAS res. there is a thin grey mucky looking fluid that is very thin and smells like WD40. I have done a bit of reading online and I assume that the PAS fluid should be bright green (Texaco 14315).
Has anybody else topped up their Disco with the wrong stuff and caused a leak? I think that is what has happened.
I have planned for worst case and bought a 2nd hand steering box but would like to get some costs back if the garage I bought the Disco from have caused the leak.
Do you have to use Texaco 14315?
Thanks,
JAK..

PAS pumps leak all the time it's quiet common. unless it's really bad just keep topping the reservoir up. also you can get a stop leak version which is basically a thicker fluid.

I know that all the books reccomend Texaco 14315 but I can't find anything on it all I can come up with is
Castrol Automatic TQ Dexron III
Does this sound right?