Thanks for the quick responses guys - it's very much appreciated.
The reason we put him into daycare was mainly because we were concerned it was a socialisation issue, so we wanted him to meet lots of different dogs and have a chance to learn dog manners in a controlled environment. The staff at the centre say he plays very well. We have been on a couple of group walks with a facebook group of GSD owners - the last one was a forest hike with 18 dogs! Ode was fantastic on this walk; he actually seemed a little unsure and was quickly "told off" when he became too much for the older dogs. He stayed within a ten foot radius of us at all times and I was very proud of him.
The issue seems to be when it's a one-to-one confrontation on walks.
Ode knows the command "watch!" which is where I hold my fingers to my eyes and he has to keep focus on my face until I release him. I've tried doing this with him when we see another dog but it falls apart as soon as he clocks another dog on the horizon - there doesn't even seem to be a point where he has noticed the other dog and is okay with it.
Our best technique at the moment (which the trainer told us to do) is to have a toy that he's ONLY allowed when on a walk (in our case a tug of war rope shaped as a duck) and we play tug of war with him at our heel as the other dog passes us on the other side of the road. Sometimes it works and he's entirely focused on the duck and the game... But mostly as soon as the dog gets a certain distance away, all interest in the game is lost and he resumes his manic lunging. It's so disheartening, tiring and humiliating.
He wears a standard flat collar with his ID on it at all times. We walk him on a Gencon collar, which is a figure 8 head collar that loops back and attaches to his flat collar as a safety precaution incase he manages to remove it (again, it was recommended by our trainer). Originally we had him on a halti but it seemed to make him much, much worse. The gencon is better and allows him to keep control of his own head while I lead him. He works perfectly to heel on it, just not when there's another dog around.
Is it common for adolescent dogs to lose interest in recall? When we first got Ode at five months he wouldn't leave our side for the first six weeks, even off-lead. He seems to have gotten so much more bull-headed and difficult to train!