[Fran Cox]

Thanks folks for the answers,
Just after I posted my questions I realised the problem was settings.
For some unknown reason I completely ignored the Deinterlace method settings. So it was set on none, set it on Blend & hey presto, no jaggy edges. Only time they happen now is when the preview setting is very low quality. So was not a Vegas fault it was the operator.
Thanks
Fran