UTM Disaster Recovery Testing Failing

I've put together a brief disaster recovery spreadsheet with the help of Sophos.

Today I tried to test it and of course it doesn't work.

This is what I'm trying to achieve:

Client rings me and says their Sophos SG135 is dead.

I have an NFR SG135.

I ring Sophos and get a temporary licence for my NFR.

I load the latest backup for the Client UTM on to my NFR using the Import Backup in the WebGui, then enter the temporary licence number.

I bring the NFR UTM to the Client, smiles all round.

We then have 30 days to get the replacement UTM.

That was the theory.

I try to import the Client backup into my NFR UTM, but it simply won't appear in the list of backups.

Sophos are now saying I have to do it via shell command?

Seriously? I spent an hour with the Sophos Support guy setting up the Disaster Recovery Test, and at the first hurdle it fails?

Can someone please help me fix this?

Cheers.