yes it's a pig of a job alright the 2 at the cambelt end are the worst, there is a Diesel pipe which you can remove to give you more room, i managed to change mine on my last 2 cars without removing anything what i did was buy a cheap spanner and bend the end so it had a crank on it, the worst part of the job i found was getting the nut's back on the end of the plugs i ended up using blue tac on the end of a screwdriver
Where there's a will, there's a way as gav has demonstrated. It all down to sheer determination. The one behind the pump is the most difficult. The strength of the skin on the back of your hands is a determining factor. Take off anything you can that's in the way, if you have several different length spanners it helps, you can sometimes just get the end on, but gav's bent one is even better. If you think that's difficult, try changing the head gasket on a 2.1 td XM
Strangely, I found the one behind the pump to be not too difficult and did it without removing anything.
I used an old socket with four flats ground onto the outer diameter (to match a spanner size) and a magnetic pick-up tool.
Once the small wire connector nut and wire has been removed the socket slips onto the glow plug and you then use an open ended spanner on the flats. When the plug is undone it can be 'grabbed' with the pick-up tool and withdrawn. Use the same technique to replace the plug.
I found that rather than use Blu-Tac to hold the small wiring nuts when removing or replacing them, the magnetic pick-up tool held them in place very effectively whilst allowing rotation as you work with the spanner.
The most annoying one for me is the one next to that one as this did require loosening two fuel pipes and clips and a bracket (from what I recall) and took more than twice as long to do.
Dave.
Xantia Forte 1.8i, 16v X reg.(09/2000) 93K, aircon