I do not teach in the UK (I have taught SEN in the US and international schools), but thought I might offer an opinion, FWIW. I would be looking to see that you found an engaging way to introduce the subject and that you had/were ready to differentiate for learning needs/differences. Also that you found a balance between having interesting activities and not having too many bits that the students will play with, throw and generally use to ruin the lesson. You can get away with that once you are the teacher and have established the ground rules, but not usually as an outsider. In reality though, I would be really be looking to see how you interacted with the students, dealt with the inevitable interruptions, arguments and piss taking and generally handled yourself. Speaking from personal experience, if you can have or develop a style that communicates an interest and regard for the students, a good deal of energy and humor and establishes reasonable boundaries with the students, then you have a good chance of being successful with that group of students. Obviously, that will be hard to develop/show in a short lesson, but if you can show them you have that potential, then you stand a good chance. Break a leg!