The Evans Q-type single seater (QA0254) shown on the left had Entry No 1 on 18/5/35 (Shelsley Walsh). The picture in question was first published in The Light Car on 28/5/35.
That means the photo was taken between 18 and 28 May 1935.
The car on the right in Ron Grant's photo appears to be the same C-type as in this picture from Rivers Fletcher's MG Past and Present. I would guess the dark car at the back of the garage in Rod Hiley's photo is a 6 cylinder car. Even with the radiator and bonnet off, the wheelbase looks longer than a C-type. The exhaust doesn't protrude beyond the tank whereas slab-tank C-types tended to have more protruding exhausts at the back due to the tail change.
I think if it were the R-type wheel, it would be virtually alongside the engine. In perspective, it's also too high in the photo. Here's a projection of where the R-type front wheels would be in perspective, working from the position of the rear wheels: