I reckon the lugs are "fancy" & based on these pics I sourced def a Holmes (not sure why you thought Youngs)
Regards
http://www.classiclightweights.co.uk/builders/youngs-builders.html
http://www.classiclightweights.co.uk/builders/youngs-builders8.jpg
Yep, I've seen those links thanks. I thought 'Youngs' as they also have fancy lugwork and I hadn't seen the pics you posted.
My dad's shop was next door to Youngs on Lee High Road and I was lucky enough to own one of their bikes (and go sea fishing once with George Young, but that's another story...)
Sadly I don't still have the bike