Sounds like you’ve given a bit of thought to this which is good.
Im not sold on the 1/2 block pier (why not full on flat?) but thats a job for your S.E.
Try and blag yourself a copy of NHBC technical standards or similar, these have lots of rules of thumb and will ensure anything you do will be passed by building control, if you abide by it of course. These are pretty expensive, but some nice fellow might of put a downloadable version somewhere on the net if your lucky…which I obviously don’t condone!!
But to be honest can’t stress enough the value of having a S.E to come over have a look and knock out some calcs, shouldnt cost too much, but will be invaluable in the long run in terms of safety of the occupants and potential re sale value of the house.