They have haunched it properly today (I didn't say anything about it, they just did it).
See here:
https://goo.gl/photos/TyNXNFhfoKGQeD4cA
They are going to put top soil down to give a "ramp" down to the garden. If it isn't any good then I can always go the sleeper route later, I may as well take them up on their offer as it's within the set price i'm paying.
Regarding the slab thickness, it's 22mm calibrated by laser cutting. Quite a few other landscapers I know (previous guy I had do my driveway who was booked up for the summer) use them and recommended them to me. I bought the slabs myself and I am paying them to lay the slabs only (not supply).
There is one slab that seems loose and I will get them to correct this tomorrow. I haven't paid a penny, so I will ensure I get anything you guys can see sorted. I have not informed them that I wanted a finished border, as in my original post I didn't expect the difference in height to be 15cm.
Does the haunching look okay now? They have asked a few things, main one being regarding the aco drains. The guys who built my extension put them at a stupid angle at the side door, so they've removed them with my permission and created slight slope in to the drain nearby instead. So they are quite receptive to my requests.
I don't know what i'm looking for in all this and if i'm honest just google the odd thing, I don't expect every landscaper to do things to the letter from pavingexpert.com