Appreciate all the replies from everyone!
In terms of design of the outside I love the image attached by Tony Holt, however ours would be on a smaller scale at around 3,000 sqft for the house size.
We haven't secured a plot yet, still very early stages.
I have experience in doing internal finishings (flooring, internal walls, painting etc ) so will aim to do this myself and also have good friends around me that do plastering, etc
So I would look to hand out trades individually rather than get 1 main contractor to complete the build.
I am still researching what would be the best build material for something like the one below.
I visited the build show at NEC in March which was insightful, and hope to go back to the one in Surrey coming up in June with the Mrs.
I think our budget would be around £600k (exc land) inc foundations for the total project - is this reasonable?