Thanks for the advice.
A 6m motorhome is the smallest that has on-board toilet facilities which is a requirement from my wife (one of her few).
I have read enough to realize that a large part of the first half of the trip will be on single-track roads. We will be starting in Oban (from Glasgow) then proceeding clockwise around the perimeter of the country - Mull, Ben Nevis, Skye, then into the northwest wilds (Torridon, Ullapool, Lochinver, Durness),, then Orkney, Wick and then following the A9 through Cairngorms to end the trip with Dunfimline and Falkirk.
That's the vague idea, at least. We have very few set places we HAVE to see. For us, this is more about being in the Scottish countryside than seeing any particular place. When we travel, cities are low priority, nature is what we are after.
I know from a European perspective this seems like a LOT of driving but my wife's commute round trip is less than the drive from Glasgow to Oban and mine is pretty close.
The first day will be the most nerve-wracking. As you said, the jet lag plus driving "on the wrong side of the road".
Why is the A82 so unnerving?