Well, Miss Lily saw the magic happening, and demanded we tidy her room. I took before pictures in hers (below), so you can see the difference.
Now, to keep it all this way. What's needed next is a MASSIVE de-toyification in both rooms. I'll tackle this when they're at school. My plan - remove 30-50% of all toys, bag them and put in shed. If anything is missed, we can bring it back in. If not, I take them to the charity shop in a month or two. There's sooo much stuff in each child's room right now, they just can't figure out what to play with.