They did display a 1/350 model back in 2014. What's holding them back?
There is information that Airfix are working on a QE kit, but it wouldn't be in 1/700. "Recent" Airfix RN subjects have been in 1/350.
Interesting that a major model manufacturer in the home of the British navy did not see fit to issue a model.
Somewhat off topic, but I was pleased to see that a 1/700 injection-moulded CV Queen Elizabeth is coming.
Life aboard HMS Queen Elizabeth