Another day, another off lead dog running up to my dog, barking, snapping, jumping up, another fuck wit owner "he's only playing, he's friendly, he's only young blah fucking blah"
Elsie is coming up to two. She is fine with other dogs if they are both off lead, not desperate to interact (would rather be retrieving tennis balls) but will meet and greet nicely, waggy tail, bit of arse sniffing and off we go.
Unfortunately when she is on-lead we have had enough unpleasant encounters with off lead dogs making a fucking nuisance of themselves that she showing all sorts of calming/fear signals when she spots a dog running towards her; lip licking, ears back, tail down, she drops down into a cowering type walk, head turning and 
hackles up. I very much do not want to get to the point where fear turns to aggression, and obviously I'd rather she was not scared at all.
As much as possible we get in the car and drive now to walks where we will be alone, or she will be off lead, but there is one walk we do on shitty weather days like today where imo she has to be on the lead (busy canal tow path, lots of cyclists) but we are guaranteed to be met by off lead dogs.
What do I do? We cannot move away from the dog as we are stuck between a canal and a hedge.
Would classes be of any help to reduce her anxiety around dogs when she on the lead? Any clicker techniques?
I am so fucking fed up I could cry but it seems a whole swathe of the dog owning public are blissfully unaware that they should put their dog on the lead when they see an on lead dog approaching. Wondering what I can do to improve the situation?