http://en.wikipedia.org/wiki/The_Original_Soundtrack
I guess I have heard most of their stuff. The Original Soundtrack was purchased by me when I was 13. Later "I'm not in love" made them a popular band and it was played 30 times a day on the radio. The Original Soundtrack made 10cc famous. It is like a pop record but very opera/musical rock opera which was the in thing at the time after Jesus Christ Superstar and Tommy. I guess they are an enigma of a band really. There later stuff was definitely not progesive in the classical sense we use the word. I really don't know what I would call their style. It did have prog elements and pop elements.
Remember too that Killer Queen was a total hit in 1975. An opera/rock number. The question could be asked if Queen was a progressive rock band?
Edited by Redcarmoose - 12/12/11 at 11:33am