Ah ok " untrimming " cool. So keep them till you are sure your finished. I'm a nurb noobie only polys and subdivs here.

I think most of the problems were me learning actually. Not deleting circles and trying to fillet them, not selecting things properly and not clicking done or right clicking to finish operations. I got the construction guides much better now using split view to check things are snapping nicely. The viewport thing was only one particular step.

I got to the end ok. I wish I'd got the 30 day demo so I could have saved along the way ...doh. I get it now for sure and do it again.

So is there a common reason for fillets with 3 edges instead of 2 ?

Thanks for your reply and suggestions, regards Wheel