Well done Boundary Commssion: 9/10
The maps are here (found on the first page of sear engine results):
I found the right pdf on my second attempt (I live very close to a boundary).
pdfimages (from poppler-utils) extracted the underlying map without any problems.
pdftotext pulled out most of the text, near enough, but there is not that much text.
The boundaries are a little more tricky. For a single pdf, I would put the full rendered image and the underlying map in separate layers of the gimp and trace boundaries into paths by hand. If I had to deal with all 500, podofo looks promising.
Most government reseased datasets are a pain to find and decode. It looks like the Boundary Commission made no effort to hide, obfuscate or encrypt this data at all. I am sure heads will roll, but if the people responsible somehow survive the inevitable pogrom: SVG format boundaries would be nice.