I suspect I have a dodgy HT lead leading to a constant misfire. I've checked everything else so this is my last option. I can't check them with a meter as my probes don't go deep enough. One of the rear ones looks iffy. Is the lead a standard item which I can buy in lengths or is it NC30 specific? Also, how do you remove it from the plug cap? I didn't want to just yank it out in case?

I believe the leads screw into the caps as per a normal thread. Give them a twist and they should unwind off the Plug Caps. As for the type of lead, you can get different gauge(?) leads so you will need to know what one you need, but you can use a length of standard HT lead as long as it is the right gauge.

Rick Oilver has a replacement leads kit in his expansive list of kickass NC kit.

Drop him a line and he'll surely sort you out

Cheers lads, will do that.