I can only add three foam fire extinguishers to BEag's tally!
That picture also reminds us of just how small and low-slung was the Gnat, and how large the fin was on the Javelin. I can't even remember what the external/visible difference was between a JP Mk3 and Mk4. Was the jet pipe tail-cone slightly larger on the Mk4?
How many of the original 20 RAF Dominies remain in active service?