Confirmed as Locust
I have been informed that these 'Crickets' are in fact Locusts http://www.rspb.org.uk/community/wildlife/f/13609/t/107241.aspx
Spotted this yesterday, I only know it as a beetle but the guys at the RSPB reckon it is this chrysolina banksi secreting, well whatever it is it was secreting some fluid on the leaves