That was the crux of the question really. It may be best to cancel it all before I leave. From what I've learnt I'm overqualified for it anyway and it shouldn't be a problem. I just wanted to keep the Non B alive in case my application was rejected. Thanks all for the input
no I'm on a non B not any extension. If you don't have a re-entry then the work visa is cancelled as soon as you leave the country. If I get approved and can cancel the current one on return then that's fine