I too was after similar feedback when I started my project. Canvassed a couple of architect friends and acquaintances but didn't get much in the way of helpful info. One said "this design is terrible, you should have given it to me to do in the first place. But maybe I'll look at it and tell you what I'd change" to which I said "and maybe then I'll give you the job of redesigning it". She didn't, so I didn't and I proceeded with my design. The other one was much more helpful even though there were only a couple of off the cuff comments about ensuite bathroom sizing, and a complaint that I'd used 45 degree angles in a building so I clearly hadn't a clue what I was doing
Ultimately, I'm really pleased with what I designed because it represents exactly how I want my house to work for what I want and I can pretty much justify every decision I've made with regards to light fall, heights, room positioning, structural member hiding, and so on. I'm sure that any number of websites can give you the basics of things to consider but:
consider how you will use your house, at what times and what physical size you want things to be. I wanted tall doorways, shallow stairs, a bathroom above the utility, a window that would let the sunset in but not shine a reflection on the TV, a sound system not under the guest bedroom, a close plan layout because my partner gets cold and sufficient doorways that I can open up a circuit around the house within which the kids can razz their go karts/bikes/ride-on-plastic-things on a dreary day. Only you will know how you want to use your house, and noone can tell you.
Personally, I'd have the stairs the other way round and accept the loss of a large understairs cupboard because I'd want the lounge to feel larger. I think I'd have also had the kitchen and diner swapped round so the services (water/****e) could more easily access the outside world but again, my earlier point: is this house you've designed how you want to live? Does it do everything you want? Is the bathroom over the kitchen because the washer is in the kitchen and you'll just have a hole in the floor to throw your clothes down? Does the morning sun stream in through those lovely bifolds and make you feel more awake as you have your cornflakes? Will you and wife be enjoying quiet and peace in the kitchen while the kids are kicking the bells out of the playroom(as far away as possible)?
Ultimately, think about everything and ask yourself if you can strongly justify something being the way it is. If you can't and you have a suspicion you want to change that element, then change it
