Wow! My first post and I got an instant reply. Thanks tt2. I thought I would have to wait ages.
In the hope of helping another newby, here's what I did (though this is probably covered in the other posts) but here it is in cat-sat-on-the-mat simple form.
1. Right click the track or album that had the artwork you want removing and go to the 'Get Information) option.
2. Click on the artwork tab.
3. Instead of clicking on the large album artwork as you did in previous versions of iTunes click in the small version that appears on the top left hand side of the requester (not on iTunes itself - which is where I was going wrong). A light blue border appears around the small artwork.
4. Press Backspace or the DEL key or Control X to delete the artwork and click OK.
Artwork gone! This worked for me and I hope it works for others. Sadly once highlighed the copy (Control C) or paste (Contril V) did not work so I couldn't copy artwork from another disc (i.e. disc 2 of a 2 CD set) but since it lets you drag the artwork to the desktop, one can import it from there. A pity that Apple did change things especially when they used to work so well previously.
Thanks again to TT2