For this one we consulted with the guru on Bicycle History, Ron Thompson, as all the other Hetchins frames we found online were far more ornate.
No interactions with Ron could ever be dull, always presenting his thoughts with gusto and a sharp sense of humour that could perhaps be described as droll – “curious or unusual in a way that provokes dry amusement”.
A few amusing emails later we sent him the photos that would help him to make a better diagnosis and we had a good chuckle at his response (and I quote):

“It would perhaps have helped/saved time and sent me on a different and more productive track right away, if you had sent me the pics of the downtube Hetchins logo, the seat tube badge and the Prugnat sticker in the first place. 
Not complaining – just a methodology for future cases.  There would be no Agatha Christie mystery novels if all the facts/relevant info were to have appeared on page one. 
As it is, the plot is revealed page by page, chapter by chapter as relevant information comes to light (but with copious red herrings along the way) until, and at last, all is revealed in the final denouement.  
It would make the sleuthing job far more likely to yield a positive result and arrive at a positive identity solution (rather than end up as an unsolved case) to have ALL relevant info (even that which you may feel to be irrelevant) provided to begin with…
Next time.”

Sheer brilliance.

He added:

“Hetchins was a ‘bespoke’ builder.  Yes they had stock frames in their catalogue…
As suspected the headlugs are a modification.  Prugnat made many designs.  This is an adaptation/”modernisation” of a stock item.”

He said we would be able to find any more information we needed through Peter Underwood and his site here (another “mine of information”) and reckoned respraying the frame would not be sacrilegious as the “Hetchins” decal/sticker should be available and bespoke frames were painted whatever colour the client desired, however the seat tube sticker/transfer looked unique.

We managed to preserve the original Prugnat sticker, masking it off, and the badge is a blank metal one which Jared painted by hand.  The Hetchins on the seat and down tube are stickers.  Badge and stickers found here 

And now for everything above in pictures: