In the end I fiddled with a little bit (the colours of the flowers) but left everything else.
I may end up doing lots of changes as I go through the blocks but I guess I can always come back to the earlier blocks and change them if they look out of place.
The colours in the above photo are a bit off because I was photographing in the fading light of the evening.
Again I used water soluble marker, but this time I just sprayed it with my ironing bottle rather than washing it under a running tap. Don't quite have the same crinkled up mess of the last block.
Speaking of the last block, even though I pre-washed the white fabric, it looks like the centre square has shrunk after being rinsed. I couldn't work out why. This month it occurred to me that maybe the pellon had shrunk! Of course I thought of this after I'd ironed on the pellon for this month. I couldn't locate any information online about preshrinking pellon (other than to iron it, which obviously doesn't apply to the iron-on version), so I followed the same instructions I'd found for whisperweft when looking the other day. I'll have to wait till next month now to see if it had any effect.
I've finished constructing all the squares for this, and yesterday I bought a larger embroidery hoop so I can do it all in one go without moving the hoop. It's all systems go!