Great Green Bush-cricket (Tettigonia viridissima)
They are quite common here in Dorset on scrub and bramble especially on the coastal cliffs and along the Purbeck Ridge. I have seen them in various places from Dursleton and Swyre Head to Corfe Castle and Creech Hill.
Although large insects their green colouring makes them difficult to spot but if you have good hearing then you will be able to pick up there 'loud' sewing machine like stridulation. At my age I can't hear them but I do have a bat detector to help me find grasshoppers and crickets. This one is quite deafening through the detector and you can pick them 50 yards away.