I think it is because there are many people in this world, including myself, who fundamentally believe that the starting point should be free trade and that the peoples of the world improve their lot generally by having free trade.
In any event, we are facing a revolution in the meat sector and it is looking increasingly likely that within 15 years cultured meat will have almost replaced low-value minced meat, chicken and pork. Furthermore, I think it unlikely that UK producers of pricey high-end meat products, particularly ones selling to local markets with strong local followings, need to fear Australian meat imports.