She sounds exactly like she's been doing DIY in her house! She seems to really like it though. She uses the middle part for her wees and then the two other parts as a nest and food hoard. The plastic litter tray I have didn't fit (bad measuring on my part!) and the rodipet one was too small (you were right serendipity!) so I'm using a little plastic Tupperware.
I've also given her a big sand bath outside her house which she uses for wees and poos when she's up and about, so her house one doesn't get full too quickly.
All seems to be going well, she is utilising her cage space really well and the chewing has basically stopped. She seems a lot happier so we are too
I'll post some photos when I'm back from work tonight.