I prefer to spin in the grease and wash the spun yarn. I've never yet found one too greasy to spin and that includes CMM.
I'm more in your camp, Lesley, preferring to spin in the grease (after a cold soak only) for the most part. However, having had to wash large numbers of fleeces for our Deb Robson workshop, I hate washing fleece - and washed fleece - less now!
And, now I've partially overcome my antipathy to washing fleece and washed fleece, I can admit that anything tricky to prep on mini-combs or hand cards may well be easier if washed. So a greasy longwool, I would wash. Manx and Castlemilk, if short and greasy, I'd wash for carding, might wash or not for spinning off the combs. Anything in between, I'd probably not wash, mainly due to time constraints and workload, rather, now, than my preference.
I still like the magic of the spun-in-the-grease yarn turning white and airy when it's washed!