On the weekend I lowered my nl fairlane superlows all round the front seems to be riding fine but in the rear whenever I hit a lump or bump in the road it goes clunk like the spring is fully compressing or something? Could my rear shocks be dead?
I just look under my car at the springs and it looks like the rear three coils are fully touching?

they will be progressive rate coils, they are meant to be touching.
to fix that clunk, get back under the car and do the bottom shock bolts up tighter.
breaker bar tight.

They are king springs if that helps? And so you don't think my shocks are dead?

try tightening the lower shock bolt first, it's really common to not have done them up tight enough.
they need to be wheely wheely tight, put yo back into it.

Alright Cheers I'll give it a shot!!

I don't know about this specific situation but i once worked on a rav4 with lowered progressive kings springs and the coils fully bound before the bump stops contacted, so the suspension bottomed relatively easily and when it did it was harsh. Kings had just made the coils, they were kind of test models. I spoke to kings and they didn't care, they didn't plan to change the spec. This was a while ago.

Many cars simply don't have enough space for progressive rate coils to be fitted, especially some japanese models that have higher grade steel that can flex more and need less room. Designers have packaging reasons to reduce the space required for suspension.