The weird and wonderful image above is the nymph stage of a plant bug called Heterotoma planicornis. This little fella will grow up big and strong and will look like the big fella in the image below which I took last year.
They grow up to 5mm (0.2in) long, and the adults and nymphs feed on other insects and plant tissue.
Rear garden, Staffordshire, England. July 2016 and June 2017.