hey thanks for that.
It was running badly (its a lemon and always is) it was getting far to much gas (to the point where it was leaking out of my newly cleaned pipes) and smoking like a train. I had been having carb issues so i changed it for my spare, after that it wouldn't start as above. something i did think of last night though was that I had replaced the gearbox fluid when i took the pipes off so it was less than a week old and it had about half gone, when it seized i checked it and realised this and topped it up. It had not leaked out in the garage or anything either.