My 16mth springer is constantly cocking his leg up new things,I know this is normal but how can I stop him, At the moment I cant take him in anyone elses house for fear of him doing it.

It seems to be what boys do, I'm afraid. Eternal vigilance is required in new places.

My boy will still very occasionally do it somewhere he shouldn't, normally where there are bitches, even though he is neutered, as JG said, be extra vigilant, maybe keep him on a lead where it would be unacceptable.