OK so a bit of a follow-up on the oil-change yesterday, at 8 months & probably about 3500km ... it was dirty enough that I felt happy that I'd done it. Didn't look much different to the new stuff on the dip-stick, but was obviously quite dirty once I have an entire oil drain pan full of the stuff (not to mention what I managed to spill all over the garage floor due to taking short-cuts that ended-up taking me longer than if I'd not taken said short-cuts). Absolutely no hint of solids & nor did the old oil feel any different to the clean stuff, and it wasn't anywhere near as bad as some of the used cars I've bought & immediately given a proper service just to feel better, but still happy I did it.