Samsung holds the Royal Warrant for electrical goods and the Royal Family won't engage in paid product placement. My bet is the MacBooks were provided by Apple to the mental health charity in a separate arrangement.
Most likely whatever media organisation were involved in this handled the technical communications and just happen to be macbook users, and they weren't going to use 5 year old beat up models lying around the office.
Nothing to see here.
The camera angles just made it so glaringly obvious, sponsored by Apple. As noted, its possible the production crew just went to the nearest Apple store on both sides of the Atlantic, picked up two base models and set them up. I must admit though, the Space Gray looks really nice.