Ann: Full Year Statutory Accounts, page-6

I don't think it is a trick, the accounting rules require you to recognize revenue as you provide the service. These contracts were sold and unearned revenue outstanding on the books was bought to book as the provision of the service was no longer required by FZO. Otherwise the unearned revenue would have been brought to book over a longer period (3 years?) when in fact everything had already been delivered. the ATO would take a dim view of that.
It may look complicated but it's by the book. You can only recognize revenue when you have earnt it. When they sold the contracts with no more service to be provided everything that was in the unearned bucket becomes earnt.