Just remember that doors mean that people will walk through them! I know, silly, but it means that nothing can be placed in front of them and you need a clear path between the door and where people are going. What seems like a perfectly decent sized room can be ruined by a through-way that limits the use of the room.
I don't see the need for those doors.
Also, I would not have the dining room/ kitchen as open plan. It's all very trendy to have a large open-plan but in reality the kitchen is a messy place, you don't want that spreading in to the new lounge. Kitchen/breakfast room is fine. Kitchen/ dining room, not so good. Kitchen/lounge, terrible. Just imagine watching TV while someone is making a right clatter in the kitchen. Also, you haven't got a utility room so the kitchen WILL be noisy.
Are you using all those bedrooms? Reason I ask is because attic rooms tend to be very hot in the summer. Not somewhere you want the primary bedroom. If the other rooms are used less then shift them in to the loft and move the master down.
Sorry fella, which doors do you not see the need for? The ones between the living room and dining room?
After a lot of debating and working around I've basically figured out the perfect usage for myself going forward.
The downstairs layout is basically going to stay as the layout above, however the living room will be my TV watching area (as it is now). It's a good sized room and it's got a great layout for perhaps one day installing a projector.
What has been marked as the dining room will have the chimney breast opened up a touch and a nice stove put in, the door on the opposite wall to that chimney will be blocked and a row of bookcases will go there. I'll whack a pair of armchairs and that will be a formal sitting room.
I'll decide where my dining area will go once the thing is constructed as I can't visualise which is better.
I won't bother putting a TV in the rear area, but will put a sofa for just chilling when it's nice and hot facing the garden.
My garage will be part utility room and part garage, I don't want to put a dividing wall as to me they're one and the same. The garage will house my boiler associated gubbins, it'll also have the washing machine, afew kitchen cupboards for extra storage and a boxing bag secured to the floor.
I'm quite intrigued by the loft room, because I haven't decided if I'm going to use that as my main bedroom going forward. As you said I need to see how hot it gets during summer but the bigger issue for me is that I'm 6ft6 and I get nervous when the ceilings aren't very high. So once the shell has been constructed I can properly assess whether I'd be OK in that room. Otherwise Bedroom 4 will be the master, that's what I'm currently in and it's fantastic size.