Don't want to scare you, might not be the issue at all but this page talks about the fix for the leaky grommets. Might be worth a little read through
Good luck!
A common fault on the engines is the rocker cover grommets failing and letting oil past into the spark plug tunnel. Take the coil pack out and shine a torch down to see if any oil has collected.
I've just replaced the diff bush with the whiteline and yip, big one in the top, small in the bottom. I first had them in as per instuctions but swapped it round and it looks straighter and seems better.
Hey MikeyM, just stumbled across this topic. You're not alone in owning a Zed on Skye, I've just got myself one. I stay north Skye too. Give us a wave if you see me on the road!