Put the hob on an outside wall run and duct straight through the wall. I have an externally mounted extract so I can get lots of extraction of cooking smells and smoke with very little noise. It is what nearly all commercial kitchens have. Not so important if all you do is steam a few veg and order in takeaways.
If there is space, a lorry mounted boom pump is a real time saver. Hire a rotating laser level. You will still need a mate to help. The pumps make a fair mess when they clean out. You can end up with a fair amount of concrete and washout, so plan somewhere for it to go.
Make sure your access is OK for the truck. Could be 3 x 8m3 loads. 32 tonne each. Hopefully the lorry can back up near the trench, maybe either end.
Ideally you want trench inspection 1st thing, then concrete early. It can be annoying hanging around then having to work late because you are not a priority customer.
If you have got the next stages planned in, with contractors lined up, and building regs / warranty people giving the OK to your proposals, you could go ahead. It is not monsoon. It has rained in this country before. You are not made of sugar.
Have you looked at loft legs? They could raise the height to give you more space for ducting, cables and insulation. It will reduce height though. I am not sure why you are proposing membrane.