JayADee:

 

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I considered replacing with a smaller dog. But I take my dog ownership seriously. Once you own a dog, you're committed...

 

If the dog in question is the one in your avatar, please can you post some pics?

Photos. You can't have him though. Except for the dog reactivity on leash and the amount of exercise he needs he's pretty awesome and well trained.

They're not made locally. Nice suggestion though. Aw, that's nice you take the dog out! We do the same for my dog's brother. He comes over almost daily for a play date. They run around like lunatics in the back yard taking turns chasing each other and dipping in the kiddy wading pool for a bit. My dog isn't a toys kind of guy. He also doesn't like swimming or retrieving haha. His brother loves all the normal retriever stuff. Mine'd make a great airport sniffer dog though, he's fantastic at finding hidden objects in the house or in the yard— like super, super good at it.

Handle9:

 

MadEngineer:

 

Do slip leads work well when a dog tries to reverse itself out of it? Our lab-cross has attempted this a couple of times (reacting to a pair of unruly dogs charging full noise at their wire gate and another where she suddenly decided to try and catch up to a dog we'd passed). I've always thought thought she could have easily get her head out of any other contraption.

 

 

Slip collars aren't made for controlling an out of control dog, they are made for training and controlling a trained dog. The way I was taught how to use it was a short jerk to the side, not to hang on with the chain. It worked very well. 

 

I can usually reduce the pulling with a couple of soft tugs on the leash which is usually followed up by her with a good check in.  I think sometimes she can smell something on the wind and will walk with determination trying to get to it quicker

I also use the stop and turn method. It works well. Calms him right down. I only started fine tuning his leash walking a couple weeks ago because he generally walked ok but due to his dog reactivity I've decided to cement it and get him walking more right beside me and I've found he's a lot calmer on walks as a result. I tell him 'go sniff' to let him know at his favourite spots that he can take the lead for a few minutes and then I'll follow him as he checks out all the smells then we go back to walking beside each other.

I've experimented a few times with pulling lightly (steady tension) on the lead until he's back at my side after the turn. So you're pulling gently forwards. I'll also sometimes walk less in a straight line—like walk in squares or ambling side to side over the footpath. As a human I have to work at remembering to do that even in a park with no path.

 I've also found walking slower works better for him being calmer (the complete opposite of the advice of a dog trainer). I also, if we hit a hot spot where he gets excited, will walk past that same spot multiple times by doubling back over it until he calms down. Ditto if we're coming up on a spot he's getting super excited about to get him past it calmly I'll walk back and forth gradually covering more ground towards the whatever it is. The other day it was to get him past a truck parked at the curb. Turns out the owner has a female lab his age so my guess is the excitement was her smell. I didn't know it was the truck he was getting excited about, just that he was getting over excited and pulling forward on the footpath. I found out once we were past it and the owner of the truck approached for a chat.

I taught him through 'capturing the behaviour' off leash to walk next to my leg when I tap my leg with my hand. So I can also, if he gets ahead of the leash, stop and tap my leg and he (pretty literally) jumps back into place because he knows I won’t move until he does. He can find that frustrating though and I don't want to stress him out so I don't do it too much.

My last dog spoiled me terribly because she was the rare dog who self taught leash manners whereas this guy is more wired generally and needs coaching.

I'll have to try that go sniff one.  Apparently the repetition of taking them past that spot over and over incites boredom so they eventually leave the distraction alone.  This doesn't seem to work very well when after changing direction they find another distraction on the other side of the footpath haha.  Dogs learn that the constant pulling seems to get them eventually to where they go - tension on leash means progress so that's what you're trying to stop.  The human should be in control, not the nose.

To answer the OP's question for this thread: If you are shopping for something and have been given confirmation after asking if an item will be suitable for x you'll be able to return it citing its unsuitability or to the CGA's term's, fit for purpose.  Post-purchase, you might be able to get them to replace it under the CGA by specifying your requirements, asking if said product will suit and if they say yes then you can point out that it's not.  Hopefully you're already getting this sorted but that might help for future reference.  Frequently a shop will happily take something back if you return it as new purely to keep your custom.  

For anyone following along…

Having tried it now I'd probably recommend against pulling gently forward after a turn (when the dog has pulled ahead and you've turned to reset his position). I think it was too aversive from his body language and lagging. 
I had my first walk where I had to do zero turns or direction changes today and I didn't realise it until we got home. 
It seems to have clicked for him. If he feels a bit of leash pressure he now checks himself.He did a fantastic job of ignoring a couple cats chasing each other that squirted right across our path in an alley.

Method of loose leash walking is described in this book with photos and details about 80 pages: My Dog Pulls. What Do I Do? by Turid Rugaas 

Or summary here: https://www.myherodogtraining.com/wp-content/uploads/2017/07/How-to-Stop-Your-Dog-From-Pulling.pdf

I sent the collar back for a refund a few days ago.