Hi jamsandwich, I have a dog of my own and I'm a dog lover but dogs barking all day would drive me mad.
Can you try to figure out if they are barking when they see or hear people walking past, or are they just barking none stop, at nothing in particular, which would be unusual.
If they're barking at noise at the front it would be quite easy for your neighbours to put them in a room at the rear of the house so they wouldn't be triggered so much.
It does seem to me that when you mentioned it to them before that your neighbour had done absolutely nothing about it.
Could you approach them by saying that you have trouble sleeping some nights and need to grab a few hours in the day and the dogs barking are making it impossible. Then you'll need to complain every other day.
If it is the dogs being triggered by noise at the front, you could then tell them what you've observed and ask them if they could perhaps put them somewhere at the back. You can be apologetic about it but say that it's making you quite ill.
If they do nothing after this, record the noise and play it to them, they may not realize how bad it is.
Then of course after that you can complain to the council and really who could blame you.
Good luck with it all.....?