Hmm, I didn't remove it, I just took the four screws out, slid the rack and the guide part out of the axle and once it was all washed out and clean I put it back together with fresh grease. I took the castle screw out of the pinion housing and the spring and the guide thing to allow me to clean it out and grease it again, have I buggered something up?

Doubt it, probably just needs the setting of the castle screw adjusting.
There would have been a split pin securing the position of the castle nut; did you put the castle nut back where it was originally?

I put the pin through the little hole drilled in the castle screw, I doubt it'd go through if I had it one turn more or less. I think I'll dismantle it all again and wash it out and fully sssemble it dry and see what occurs.

Have a look at the pinion. It makes sense to remove it now.

You're right, I don't want to do it again when the car is back together, rather get it right now. Do I just drill the staking out and unscrew the bottom of the pinion thing?

Yes bore the peening away ( 2 places ) and unscrew the pinion nut. The pinion is under load from the rack itself and need twisting to get it out. Putting it all back together, you need to remove the adjusting mechanism on the other side ( screw cap, spring and cup )

Thank you, I'll do it at the weekend.