Companies do not go bankrupt in UK law. Only private individuals. Companies get made insolvent. It's essentially the same thing as US bankruptcy but the wording is important.

Administration is when a private legal firm takes over the business and runs it for a short period to decide what to do with it. They are impartial and have to act in the best interests of the creditors (those that have money owed to them by the company). Normally this means shutting the business down and selling it's assets to cover any outstanding debts. However if someone is willing to buy the company then the administration firm will run the business until the buyout has gone through.