G-ASKK (PP-ASU) was originally CF-MCK but the order was cancelled.
sources:
http://farnboroughspotter.weebly.com/1962.html (but with spelling mistakes!!)
https://www.airukreunion.co.uk/portfolio/herald-fleet/ (Row 9, centre picture)
Also I have poor photo of an underside view whilst it was demonstrating at the 1962 Farnborough display, which I logged as CF-MCK at the time.