The collar is the issue here, specificaly the left side pulling away at the neck. Sloping the shoulders more is not the correct thing to do. I can't discern much from these pictures. I am suspect that your left shoulder blade is more prominent than the right, A picture of your shoulders with the jacket off and a shot of the jacket, front and back with the jacket unbuttoned would be useful.
They may have to cut the shoulders differently and adjust the front back balance.
I believe the issue may be that the shoulder angle is cut for the low side (right) and that the left shoulder is 1/2" squarer lifting the coat at the shoulder point and pulling it away. The right side is probably your strong side and the chest more developed, the left side is less so and needs to be crookend on.
In short release the shoulder 1/2" on the left squaring it and crooken 1/2".
Don't believe prominent blades would cause such a severe issue but then I always stretch for blades.
Terpo, it occurred to me you may be interpreting shoulder slope differently than it is intended.
Sloping the shoulder line is lowing the line at the shoulder point where the sleeve joins, making a greater degree of slope. Lowering the shoulder line at the neck is squaring the shoulder. The degree of slope is diminished making the shoulder line more horizontal.
There are other times when it is better to raise the point at the neck to create slope or raise the shoulder point to square the shoulder but don't want to complicate the example.
Your left shoulder is too sloped and needs to be squared at the neck by lowering the shoulder line at the neck. Think of the shoulder line as a plane and the center point, from neck to shoulder tip, as the fulcrum. it is too low at the shoulder point and makes the collar stand up at the neck. This adjustment may be enough to correct the collar standing away but your left shoulder blade may be contributing some.
Thanks for the feedback, Despos and Rory Duffy.
I am not entirely sure what was done with the shoulders, all I remember is the gent taking my MTM measurements mentioned my sloping shoulders and then pinned the neck to do so. I believe the point at the neck was raised. The term I used to describe this was probably inaccurate. Thanks for clarifying! :)
I also took some more pictures with the jacket unbuttoned and without the jacket: