Mooching he's 2yrs 6months. No, no more funny turns and all tests came back normal, the vet mentioned something about "gundog fatigue"

....a sudden drop in blood sugar. This actually would have made sense as he hadnt eaten that morning (he was given a meal but didnt eat it). We always make sure he eats something now and carry a snack just incase.
Yes, I think what set it off was a run in with a particularaly nasty terrier...same one that bit my eldest daughter if anyone remember that post? I think its since then that he's been more troublesome on the lead.
Karma that makes perfect sense, thank you. Have just walked him and tried a high value treat on the end of his nose and the "leave" command - that seemed to help.