The chances are your situation is completely above board. However, there is a minute chance that you are being conned, but the chance is negligible. You cannot guard against this paying 6 weeks in advance (a trifle cavalier by the apartment owner, I think).
Furthermore, you are doing business with a person living in the UK whom you may never meet. Remember, the apartment owner is also trusting you. What is stopping you from stripping or wrecking the apartment?
It comes down to goodwill and trust. It works both ways.