Hi Peter and Kevin,
One of my first bikes is a 1958 (57?) Holdsworth Whirlwind. On that date only Agrati dropouts were available on Holdsworth frames. The company was the first official Campagnolo importer to Great Britain about that date, so any Holdsworth from earlier will not have Campagnolo dropouts. Since the Holdsworth frame on ebay is 1970 (I didn't see the auction) doesn't have Campagnolo drop outs, it would seem correct to assume it was a second tier frame. Because by that date Campagnolo was the norm on British frames.
New York, NY