Thanks again all. I did what speedygonzalez suggested last night and here's what I found.
No other recordings are on the HDD. Timeshift is off. I started with 487gb available. I recorded a 30 minute HD prog. Looked using Filezilla the size of the recording is 1.11gb.
I pressed the PVR button it said 93% / 435gb remaining. Using the Menu/Information/Devices it said 445gb was remaining.
I deleted, waited several hours before checking and whilst Filezilla shows nothing my HDD available space remains the same.
I had to reboot and in doing so for some reason I've lost all my epg settings, yeah all them days (see other forum).
I don't know if this means anything but the pvr button now reads 99% but only 464gb available, devices method says 475gb.
I really don't know what to do now.