Semi basement passivhaus

[Clc136a]

Hello all! First time posting on build hub but I’ve been reading with interest on lots of topics! 
We’re planning an into-the-bank 230m2 warm roof L gable design and trying to tap into as many sources of experience as possible...

Its lias brown clay from the soil survey in a garden plot and originally we’d assumed contiguous pile wall and piled foundations and beam and block and cavity wall - architects idea... Latterly I’m pretty convinced (subject to SE report) after conversing with the basement expert the best and cheapest way is a waterproof cast in situ semi basement with external insulation. I was thinking foam glass aggregate, particularly under slab as it’s free draining, but transport from Germany means it is both costly and has a higher carbon footprint than EPS so I’m swayed towards a reinforced raft like kore and drain around the perimeter. We’d then have starter bars and then cast waterproof walls for the 2.5m into the bank, then maybe 600mm EPS blocks wrapping the walls before drainage membrane and backfill. I have modelled it in PHPP and had a certified passivhaus consultant check the numbers. Some of the elevations are timber clad, others ‘were’ stone facade but might change to something less complicated for external insulation model. I’ve talked to Optiwin about windows and doors, any comments? And a few Velux quin roof windows. Very interested to hear peoples comments and suggestions. Think we’re ok with the internal layouts but might post later on this. Thanks, Chris