seasons greetings,
I know this isnt what was asked for, but I thought I`d mention it anyway.
as getting the plug out is a nightmare
I found the plug spanner supplied in the origanal tool kit works well with a slight modification,
first remove the rubber plug that grips the plug.
shorten the spanner by about 1/4in. (5mm)
drill a second pair of holes for the tommy bar between the existing ones.
add to your tool tool kit a short length of rubber tube/fuel line, that is a snug push fit onto the plug insulator.
now the technique.
losen the plug by a couple of turns, hence the extra tommy bar holes.
remove the plug panner.
now use the rubber tube to push over the insulator on the plug and unscrew and take out.
to refit reverse steps
cheers Eric.