Hi,
Honeydoman, sorry , I didn't mean to take your thread off topic. Lancashire Fusilier maybe you want to cut and paste all of this into a new topic?
I generally would build a box (kick box) to be the desired height of the base board. Assuming you have base board otherwise make the kick board whatever you desire. Once you have this level, and square using shims (wedges) Try to support it in several places. To hide the gaps you then run a skirting kick board / base board scribed around the box. Use one box to put all of the seperate shelf or cabinet units on. That makes it easy to get them all lined up and attached to each other. For that reason alone I use this method even if a floor isn't way out. I have never found any install location that was right on anyway. It also helps make them into one unit, and more likely to all move together with house movements.
You can even use this box to square the cabinets to a wall by pulling one end or the other away a little if need be. In effect squaring the visible corner of a room after you have got them installed.
Seth