Adam - I'd certainly concur with your IDs on the ERAs: I have the same numbers in my records.
The #2 car looks like Ian Nickols in the ex-Parnell K3 c/n 3011. But I have that car as #7, I think from another photo. 2 would fit, though, given that it's an 1100cc car: I have Dodson's Maserati as #4 but no number for Wilson's ERA or Hampshire's Riley (DNA)
From the paint job, I'm pretty sure the car disappearing into the mist is the Brooke Special of Leslie Brooke.