Well, after completing the first dirty job on the car (you should try it Gary, it's far more satisfying than getting someone else to do it) I was feeling pretty pleased with myself.
I got the PAS filled up and air out of the system as per the manual - turning the car over a few times while turning the wheel, and sure enough the assistance soon became apparent. While it's up on the jack, I thought I'd quickly try to get the lower turbo heatshield bolt undone, so with a 10mm spanner and tube for leverage, heave hoe and BANG! It was at this moment, I realised that adreneline was brown and smelly. The whole car shifted and I could hear my heartbeat echoing off the garage walls.
I'd increased the height of the jack under the sill (what a crap system) to get better access to the steering rack and turning the wheel had obviously shifted the jack and the small extra movement when I wrenched the heatshield bolt had caused the whole lot to slip. Furtunately the axle stand had done its job but the compression of the suspension let it go down uncomfortably far. If it hadn't, the wheel was still under the sill ready to stop it hitting the deck but thankfully it didn't and no damage was done.
I could have kicked (killed?) myself, as normally, whenever I work under a jacked car, I check everything (not just the main jack but the fallback measures I always use) making sure they are still in place every time I get myself under the car. This time, the euphorea of sorting the PAS and the sudden thought to break the heatshield bolt had got my bedy running ahead of my brain and I nearly had a major disaster. If you read this, please remember it for the next time you're working on your car.
Geoff