Having done this as well but not to such a grand scale, my observations are;

The lower horizontal sections, I would not have fitted them as it makes sliding stuff in and out from under the bench a fiddle but as you are going to have drawers and or a lower shelf it probably doesn't matter.

If the garage is not heated be weary of using kitchen cupboards. I did this, they got damp and fell off the wall

Bolt the fucker down to the floor


But really nice work there I'd be chuffed to bits with that.