Extension slab at ground level

I am planning a 10m2 ensuite extension to a brick veneer house with existing timber framed floor. However the area of extension has been built up level with the existing floor. I am proposing a slab, but I am aware it must be 150mm aove ground level, which will not work. Can I:
A: Build in a drainage channel around the perimeter to achieve the 150mm.
B: Excavate the surrounding area to below 150mm (with drainage) and if so, how far back will this need to extend.
C: Build a brick veneer wall with bottom courses waterproofed
D: Build a say 3 courses of brick, waterproofed inside and out, with a timber framed wall above (due to space consideration a single wall is preferred, if possible).