in my professional opinion the issues are:
1) the set back isn't enough, it needs to be 1 to 1.5m to pull the foof line down more, this gives you issues on the internals but my view the internal door location from the hall is not a great location as the makes the houe a large u shape so study is remote from kitchen
2) the windows on the front of the extension are too large compared to the original house, this places greater horizontal emphasis, smaller ensuite window and bedroom window would help, maybe two bedroom windows and setting these out so they read beter with the garage
3) can always go 1.5 storey so the roof is lowered and you have dormers, downside is the roof pitch impacts in the room
4) if you look at the floor levels between the garage and the dining room there is a large level difference so struggling to see the point of the door
Thanks for the advice
In response to your points....
1) I hope it doesn't come to dropp[ing the roof line more as it would reduce the internal space as you say. The door from the hall really is the only place it could be into the new extension. The stairs run up the side of teh house and the brand new kitchen is on the other side and I'm not knocking that down!
The study is supposed to be as remote as possible
Need to get some space between me and the kids when I'm working
2) I'd like the windows as big as possible but I do know what you are saying. I'll see what happens after the 1st submission to detrermine if we need to reduce them
3) Don't want dormers or lower roof. I've got 2m high wardrobes to fit in the new bedroom so need the height!
4) The door into the garage is needed as it's not really a garage, it's actually my workshop and I'll be buggered if I'm going outside everytime I want in to it for some tools!
Cheers for taking the time to leave those points wigit, it's good to know what I might run in to with planning officials