I have heard but cannot conferm that the extra .5mm wont help any more than the 8mm.
The 8mm are better than the 7mm, but I think thats where it stops.

 

The real way to get it done is to make a diagram of the coil packs and plugs which should be done as you take off one wire at a time. Then on the install, start with the middle lower, than the outer lower, middle upper and finally outer upper. Decided to take off the aftermarket wires lately and install stock oem wires, and by doing it this way, I did them in under 30 minutes.

 

Typically when changing wires you do one wire at a time to ensure you don't get any wires mixed up and you get them matched correctly. Unfortunately I don't feel that this is the best approach when changing the plugs on the Disco.

Here's what I'd recommend:
-Get a helper with smaller hands than your own. Wife, Girlfriend...pay a local kid...whatever you've got to do.
-Remove one wire at a time and label it, drawing your diagram along the way. It doesn't hurt to check the original specs also because it's possible (although unlikely) that someone may have changed the wires in the past and screwed them up somewhere.
-Install the BOTTOM ROW of wires first. If you try to install the top wires, they will get in your way when trying to get to the bottom.

When you look at the diagram and see which wires go where, you're going to have to strategize a little to avoid shooting yourself in the foot. Routing the wires is a pain in the butt.

There are some other threads here about bending a screwdriver and doing other stuff. I just had my wife install the wires. It's her ROVER, she needed to get her hands a little dirty.

Install your new plugs at the same time. I would guesstimate the job taking 3 hours or so.

The alternative is removing the intake manifold...which seems like it would suck far far worse than just getting someone with small hands to do the dirty work.

Too bad nobody has come up with a way to relocate that coil pack...poor design IMHO.

 

Imdoing my plug wires right now just taking a brake to allow for the blood to dry I think Im going to take a lok at that spark plug wire wrench

 

I had no problem doing mine, took about 1.5 hours, and I have big hands. I'm also tall, and can lean over the engine pretty easily. It might help to stand on something to get better leverage. Then remove everything from the left side (wire bracket, iacv, and that random plastic line with its corresponding bracket) then remove all the wires and use this diagram to put them back in, starting with the bottom inner wires and working out, then up on the coil pack. Its easiest to reach the left coil pack from the left side, and the right from the right side. Sometimes they can be tough to get off. I used a short pry bar to pop some of them off. Other than that, try using different hands and different positions, and they should all come off. When the wires go back on, they "click" real easily into place, just make sure its seated correctly (you'll feel it slide on, and you might have to wiggle it a bit as you lightly push on it to get it to seat right).

Coil pack to spark plug wiring - Land Rover Forums : Land Rover and Range Rover Forum

 

You need to make one change in how you exchange the wires. Remove all the old wires first and then start reinstalling the new ones, while standing on the passenger side, start with the lower row, #7 and work your way to the passenger side, then go back and install the top row, the same way. Much easier that way.

 

i finished replacing my wires it actualy took m 2 days mainly because the sun would get up to high and would start to get hot. Any I ended up taking them completely off twice because of crossed wires but once it all came togeather it runs great better than it has in a long time. Thoses were the original wires I tok off at 130,00 miles and I can tell the differnece. Well good luck to the next person take your time and have patiencce it will all come togeather