I’m currently building my own house. Huge for me, but relatively modest compared to most Grand Designs, 10m x 9m footprint, it’s looking like we’ll be all in , including internal fit out/furniture for less than £210k. We’re currently almost watertight (2 windows and the patio doors to be fitted, when we finally get them – the Company went bust 3 weeks ago), fitting out the inside now.
From my back of envelope figures, we’re currently at around £160k, the external brickwork is the only remaining large bill (£10-15k), possibly some tarmac at £5-7k too. Then its flooring, wall coverings and external landscaping to get rid of the piles of waste soil and raise the ground level around 300mm. That should take us to the £200-210k level, so if managed correctly I can see how they did their large build for £630k.
Oh, we’re not skimping too, really well insulated, ASHP, Neff ovens (note plural!), nice large bathrooms etc. If it was a budget build I could definietley do it for less than £200k for a four bed, 2 bath detached. Of course, I’m not taking wages out of it, so that would be a £30k cost on top, even then, its easily doable for well under £250k.