Tørm (Torm Cycling). Nice, and not pricey

Low temperature & low agitation washing should keep you at c) for a while.

Wool shrinks as the cuticles in the fibres rub against each other, catching and holding on to each other, in the same way that felt is made. This process is exacerbated in hot water, and with more movement.

Unless you hand wash each and every time, wool is going to shrink & felt eventually.

this is spot on...felting

I'm paranoid and hand wash all my merino apart from my socks which I don't really care about...

You can stretch wool too, water, iron, pull, iron. Supplement water with tears when you've accidentally put something in the 90'C wash...