Thanks Prism99, I appreciate your input. You could well be right on the way the thread is wound, I hadnīt even thought of that. I know that it causes a lot of trouble in my machine.
By the way I always clean out the bobbin area thoroughly, so its got to be the type f thread as I use the same in the bobbin as well. As soon as I go to another thread it stops breaking and tangling at the back.
Elle