The reason for stacking is usually when you can't fit the WM and TD side by side. As you can, that's why I wouldn't bother. It also gives you worktop as well.
I've tried to draw a pic. I've put the two next to each other, suggested worktop on top along the length of the 200mm wall. Then on the back wall, I would have a run of tall but 300mm deep units. These could be full height or one full height (e.g. In the left corner) for stuff like the vacuum and base units plus shelves in the middle.
I'd also try and get some shelving where you were planning to put the WM/TD which face into the landing.