Many thanks to Giftrub and Steven for those very comprehensive resposnes. I very much agree with your analysis.
Re the St Columba in an earlier posting, she was delivered in 1977, not 1975, and the Hengist, Horsa and Senlac were delivered in 1972/3.
I'm old enough to remember the Lord Warden, on which I had possibly one of the worst sea crossings ever to Dun Laoghaire in 1979. Then again, a return trip on Pont Aven last May from Santander probably was the all time worst. I don't think she's a particularly good sea keeper and would be interested in anybody else's view.