A photograph of G-ARYG taken 3 years before the crash can be found on
Welcome to Air-Britain
Sorry I can't post a direct link.
There's also a Flight article on Strathallan Air Services here
air charter | flight international | strathallan castle | 1964 | 2301 | Flight Archive
Interestingly they promote their Helio Courier as available to any client who can maintain a strip of 200 yds x 20 yds!!!