Evening Graeme,
I'll try for a bit of Sidestrand?
Saw this on the net, although the struts don't seem to match...
It is a Boulton & Paul Sidestrand III Well done
I think the strut mismatch is due to the fact that my "bit" is looking towards the fuselage, whereas the shot you found was taken from under the fuselage looking outboard and the cowling/exhaust pipes are identical to the the one in my source (see link below). However, I do believe that the caption is wrong because the Pegasus cowlings, possibly trialled on the III, but fitted to it's later development, the Overstrand (as mentioned above by David) show numerous"blisters" over the engine's rocker gear.
This Sidestrand was fitted with Bristol Jupiter XF engines and tested with "The Boulton and Paul Townend Ring" combined with an exhaust collector (see link below)
1930 | 1346 | Flight Archive
Noyade has control 