Thanks to everyone who has been praying.
We still haven't heard back from the DWP about moving to PIP.
We managed to get some help filling in the forms - which was a small miracle in itself. We manage to get the forms in with a couple of days to spare, and within a week had a phone call to ask if they could do a home assessment. This was a nerve wracking experience - but I had a nice assessor, who didn't seem to mind that the house was a building site! That was nearly three weeks ago and we're still waiting to hear if the application has been successful. Maybe this week? Or the week after? We don't know.