Yes, I think probably best not to engage them, though even the unhelpful comments have highlighted missing areas in my original post (much more thoroughly covered in my email to FCC), I didn't actually expect such a response so didn't take much time to explain myself before posting - rookie mistake, will try to improve if I post again!
Thanks for your post, I'll mail a hard copy of my email to their physical address. I'd also forgotten about CCTV, the company will be able to verify my report visually which is great news!
Thanks again, Lindsay