For British riders in the Tour from that era I thought of Barry Hoban and Brian Robinson.
Here's a British racing history blog that mentions many stars from this era with links. Mostly links to Wikipedia pages without photos, but it may help find photos (to compare to your ad photo).
Mitch Harris Little Rock Canyon, Utah, USA
On Mon, Apr 14, 2008 at 4:23 PM, Dr. Paul Williams
> Evening all,
> Please excuse my ignorance, I am sure this is a classic image, but in
> the May issue of Bicycling there is a Camelbak advertisement (p. 53)
> which shows a bespectacled British cyclist on one of the Tour(?) stages
> in what appears to be the 1950s or 60s. He is decked out in Wearwell
> gear with Union Jacks on the shoulders of his jersey. I can't quite
> identify the bike either. What interested me, in particular, was the
> shifter(?) on the bars as well as one on the downtube.
> It always irritates me when images are used without any indication of
> what they are or from whence they come! Anyone know?
> Paul Williams,
> Ottawa, Ontario, Canada