Brambles, that was exactly what I was after. Incidently, the white border it creates could do with having a bit more white, how would I increae this, and how would I change the border colour to say blue ?
Make your selection as before - invert - now go to the little Black & White icons on the left hand toolbar. Click on the White one and the colour picker will appear - select a suitable blue - then CTRL + del as before.
There's not a better White than the default one but if you are printing it won't matter anyway because your paper will be the background white.
Hope this helps I'm only a 74 year old Photoshop enthusiast - not an expert!