Hi Andrew,
I just thought I'd say that there were some posts about this towards the end of last year that I found really helpful in training my ESS, Bear, (same age as yours) so have a dig on the forum for similar topics...
In case it helps, we went for the classic 'stop every time he pulls' as we were aiming for loose lead walking rather than walking to heel. If the lead went taut, I would stop still, and say nothing until he either came around to my side or shuffled backwards towards my foot. The moment he started to get back in line I'd verbally praise massively, and whilst walking loose lead I'd also praise. The moment the lead went taut again, silence, etc.
The first few weeks were a challenge, and it took us an hour to do a 20 minute walk with occasions of standing still for several minutes whilst he scrabbled around my feet for a scent. However, it's 2 months later, and after the first couple of minutes of a walk now, (when he's sussing out that he's on a lead, not off...!) he walks beautifully loose lead 90% of the time, even in fields and woodland.
There's so many techniques, and this one might not be any good for you personally, but we've found it fantastic - the reward for Bear is the walk, so stopping the walk is the worst thing, and starting it again is the best reward. As a side-bonus, it's also really increased my patience levels!!!
Hope you find the solution for you and yours,
C