This would have been done when I converted my FAA CPL(H) to EASA - would this count?
No, the verification process has a time limit.
The CAA has published an Information Notice
IN2017/029 with the requirements you must follow in order to exercise the privileges of an ICAO licence on a G Reg EASA aircraft.
Para 3.3 is interesting bearing in mind Article 17
Extra-territorial effect of the Order
17.(1) Except where the context otherwise requires, the provisions of this Order, in so far as they apply (whether by express reference or otherwise)
(a) to aircraft registered in the United Kingdom, apply to such aircraft wherever they may be;