Well cityfibre are the network providers and you need some one to act as an isp on the network to connect you, I went with noone internet as they provided a static ipv4 and ipv6 without cgnat, then they got bought/merged/billed not sure which by hometelecom. New customers don't get a static ipv4, existing do. I haven't noticed any type of blocking but that might just be my isp.

Most of the main providers do cgnat, mid contract price rises and generally questionable things. The one thing I was a bit concerned about was the pppoe connection rather than DHCP, but is doesn't seem to have made much difference.