So I have tweaked the design slight to accommodate some better features, and utilise the ceiling height a bit more.
Firstly, each side will have a divide in the centre of 8 drawers, meaning the draw width is only 80cm (taking away any strength issues with the drawers). The bottom two sets will be 25cm deep draw front, likely resulting in a 20cm draw for shoes and bags. Next two will be 20cm deep giving a 16cm draw depth. Finally the top 3 will be smaller and shallower drawers for small items.
This gives a maximum drawer height of 120cm including the carcas being 10cm off the ground which is comfortable. Allowing 120cm for hanging height on the two shorter rail spaces, this puts the total wardrobe height at 240 which also happen to be just shorted than a single board of MDF.
A third hanging space with 180cm length for coats and the GF's longer playsuit type clothes will allow space for two shelves at the base of the unit. I am going to use pull down rails so that my GF can get to the clothes, they also make putting clothes away a dream as they sit at the bottom of their motion.
This is the view without the drawer fronts on. I plan to use side fixing soft close draw runners. Some sort of plinth at the bottom and cornice at the top. Next I will look into which bits I should build in what order as given the tightness within the walk in area I will likely build sections and then final assembly in there.
Let me know any thoughts or better design tips please!!