Well, the new battery sorted the running out and she goes fine. I then noticed the throttle sticking on,.... just a bit now and then.
Carb off, cleaned the slide and everything, put back together and it was stuck solid. As I loosened the manifold bolts to take it off again I heard the slide drop down. Weird, but if I over tighten the manifold bolts the slide is stuck and if I just nip them up its fine. I can only assume that the tightening of the bolts distorts the body of the carb somehow,....... strange I think.
I have to say, its been a lot of years (30) since I tinkered about with bikes. Loving it though, its almost as good as riding them.