Having a similar battle with PE myself at the moment, keep appealing on grounds they're almost obliged to refuse. At the moment it's about 50/50 between appeal allowed and having to go to POPLA but they have yet to submit any evidence to POPLA.
Have they only just realised this? The problem was the assessment not the company! That said many assessors were devoid of compassion or communication skills.
For reference BC sending new paperwork to an OLD address
My complaint was lodged with the ICO
ICO upheld my complaint and have asked BC to investigate
BC have written to me to say that they have been contacted by ICO and are investigating.
I think you should lodge your complaint with ICO. The more people that complain when they feck up like this the more pressure it puts on the ICO to act