Thanks for the feedback ..
My car makes about 320kw at the engine .. and at the moment I have a OSG Twin installed.
Now after 13,000km it started slipping in 4th/5th. I think the stop and go traffic killed it since the plates are worn.
In an EMail OSG said the clutch is more geared towards harsh engagement and would wear used 'normal'
The OSG refresh kit would cost me around GBP 450 plus (taxes, postages etc)
The Nismo Single GBP 710, the Nismo Twin GBP 1,140 (all plus)
That's why I was thinking just getting the single to get a bit more life out of the clutch.
I also never liked the rattle of the OSG twin.
On the other hand just buying the refresh kit would be the cheapest option.