Well, looked into this a bit more to find some people had issues similar to this and changed the water temp sensor. this then sorted the issue.
Done this tonight but no... still VERY smoky runs a lot smoother now though
Thinking I'm going to be left with no choice but to pull the cylinder head off and see what's going on!
Might just see if I can find another head first, get that refurbed with new stem seals, pressure tested and a new head set then just do a swap rather than take this one off, check it then fix it then rebuild it.