Manual recording radio 4

[Obfski]

Hello all
I am attempting to record the "When John met John" programme tomorrow morning on radio 4, and as this is going to be a weekly series I have set the parameters to record weekly. When I try to enter and set up the recording process the Pace Sky+ version2 box tells me there is not enough space on the system to carry out my request and I must delete something. Now my wife has several films recorded, but there is 72% free on the HD. Surely a one hour radio broadcast needs less than this? Even if I set the broadcast to record only once as opposed to weekly nothing changes. I am not allowed any other option other than deleting something from the HD. Anyone with any ideas? assuming I've not sent you all to sleep with a Friday morning ramble