Demon is their in-house ISP. Not well regarded, like BT with BT Wholesale.
I recommend either vivaciti LLU Unlimited
or xilo/uno Pro 16
Note those are the only C & W products for each. All are "up to 24Mbps" depending on line length and condition of course, not limited to 16Mbps although xilo looks that way. Also note that the Pro 16 Office is ex Vat.
You can also get the vivaciti Surfwise Complete, and the "phone for info" Xilo/uno equivalent, but those are Full LLU where they take the line off BT so migrating out is a pain. They are Opal Wholesale from TT. Again the same syndrome applies, the TT line management does not apply to the Opal offerings so resellers are better than in-house.
My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost
. Internet connection -