When I sold Holdworthy frames in the 60's I found no evidence of Raleigh type "gaspipe". In fact even the lower price Freddy Grubbs were made of drawn tubing, Reynolds grade A.
You may be able to confirm this by feeling the inside of the seat tube and down tube from the bottom bracket, If seam welded you will feel the seam.
I always thought the cheaper Holdsworthy names were in front of Raleigh Carltons, they spent the cost on better materials rather than acres of chrome.
Keith