Now the rain has stopped, I changed them today with no problems at all.
The main thing is to get an extension set with wobble ends a quarter of an inch.
If you can get hold of some long nose pliers and a universal swivel for the extension set this
I only had to remove a fuel hose bracket, which was just 2 x 10mm nuts, then gently moved it to the side while replacing plugs 3 and 4.
Above shows the bracket off the studs.
I then pulled the plastic tube type caps from the ends of the plugs and added a drop of oil.
Then simply attached the 10mm deep socket onto a wobble extension and unscrewed taking care by adding a drop more of oil when the unsrewing became tight.
I then added some copper grease to the new plugs, as above.
Number 1 required a little more thought as access was restricted. I managed to add the deep
socket on its own by threding it in with my fingers from behind. I then used a universal joint type ratchet to obtain the bend and unwound. (these come in a lot of good socket sets)
Though when tightening up the new plug I managed to go in from the top with just a 9" extension.
I had to stop and start the engine a couple of times before the glow plug light would go out,
but hasnt been on since.
Total time, 40 minutes, Could be done a lot quicker, but I was very careful when unscrewing and left the oil for a few minutes.
I hope this helps, it did seem a little daunting to begin with, but its amazing how easy these jobs are with the correct tools.