This link with some great history of the British Holdsworth cycling brand, and other famous names in UK cycling, says the address of 69 Highbury Park was listed as a Holdsworth shop, managed by D.E.S Kirby, which was first listed in the free catalogue Aids to Happy Cycling of 1937 (printed late 1936).
Holdsworth
So unless Mr Kirby was doing his own cycling related activities on the premises before being associated with Holdsworth, it seems 1936 could well be the earliest date for the frame refurb. That's only my guess though, I'm not sure.