I was also at St Mawgan when 'The Slivers' arrived. Standing looking out of the OM windows down the hill when I noticed a flash of light and two smoke trails below the level of the mess which rapidly became the two 104s coming up the hill - a sight to behold. Some years later they displayed at Odiham Families Day, and I also have a photo of them coming along the crowd line just as low and close as the picture above - unfortunately I was using a telephoto lens and all I got was the nose and intakes (and the heads of those around who were ducking!).
IIRC the Arrows display at the same St Mawgan airday was even lower over the airfield than the Slivers - certainly could only see the tails of the Gnats going past in front of the crowd line (someone said their min display ht was 20ft at that time!).