Found these three while helping out with a plant biosurvey at Painshill Park, Cobham, Surrey. Pretty sure they are Orthoptera family but I've certainly not seen anything like them before. Also a little confused as hind legs are stretched out rather that the standard "bent" grasshopper position.
These are mirid bugs (Hemiptera: Miridae), which is a large and variable group of True Bugs. These are nymphs and I would plump for Leptopterna dolabrata as seen here on the fabulous UK Bugs website - a brilliant resource!