Gaz, looks as though they both had eyes on overtaking you. Were I one of the cyclists behind, unless you were signalling left I'd have stayed back and rolled slowly through behind you in single file. They obviously weren't looking past the respective person immediately in front, and therefore not reading the road situation as a whole.
The moped is being rather impatient there and should have stayed behind the car in front indicating left (who didn't left him/her through).
Ultimately when the roads get congested like that there's not much to be gained by overtaking other cyclists. Best to chill, and if one wants to light up the legs/overtake, wait for it to clear. Likely everyone will end up at the next set of lights :-)