Chromatomyia lonicerae
Mines of this species were pointed out to me by Graham Moates, although I see that the two he has had verified via iRecord are different examples to the one I photographed. In fact I think there may be two mines on the leaf I've photographed - it is certainly more complex than the ones Graham photographed.
Chromatomyia lonicerae leaf-mine in Snowberry, Wendling Beck Environment Project (Norfolk, UK), 31st July 2024