One observation is that ACAT were surprisingly unimpressed by not particularly complicated though technical arguments presented with evidence by intelligent non-experts. They do seem keen to prefer the cognitive shortcut of having a credentialed expert give sworn testimony, rather than follow an argument.
So, if you are arguing that some repair or maintenance has not been adequate, it might be better to have an expert witness assert that rather than assume it is sufficient to have a straightforward but slightly technical argument from an intelligent amateur (i.e. you).
Eg. it might be obvious to you and me that a pipe is leaking and we might think a photo showing drips would be enough but it might be better to have a licensed plumber tell the Tribunal that the pipe is leaking!