I changed the pedals but no change, the noise is still there. Stood on the pedals and the noise remained. Sat on the saddle, pedaled hard getting the noise and just lightly guided the handlebars and still got the noise. So: if it isn't those things and if it really isn't the BB then the next thing is the chain I suppose. It's new and the chainring and rear sprocket have been reversed. I still have the old chain so the next thing I guess is to reinstall that and see if there is any change. I'm off on a trip tomorrow so it will be next Tue or Wed before I can make the change but I'll report back then. In the meantime if anyone has further suggestions I will be glad to give them a go on my return.
Thanks all for your help and encouragement so far.