This is a picture of a vain grasshopper, who wanted to be photographed, as a lot of his mates are shy, and keep moving around the grass stem, in an attempt to hide. They are difficult to spot, until they jump about.
This one was about 15mm long, and is probably a Common Green Grasshopper, but there are 20 or 30 varieties found in this country
They make the chirping noise you hear on hot summer days, by rubbing the hind leg against their wings.
Grasshoppers are only active during warmer weather, they feed mainly on plant material.