canadian on a london-bejing-london short trip

My partner is a pilot for a commercial airline. He will be flying for his job to Bejing from London and back in the following week. I would like to join him. I would be travelling on standby ticket which means not a paid ticket but I have proof that I am travelling with the standby ticket confirmation issued by the airline company. I am Canadian. The trip is London-Bejing-London. We sleep 2 nights. Is it too risky? Can I use the 72 hours transit visa? Thank you