BROKEN BOLTS ARE OUT!!
Thanks to you,Keith! The Dremel tool and screwdriver worked like a charm on two of them. The third had broken too far down into the hole so I had to drill and extract. Took some persuasion - I was afraid I was going to break the extractor - but it finally gave. Great tip! Saved me a lot of time. The threads all look to be in good shape but I will follow advice and freshen them up with a tap.

Tropical Buzz