Plusnet Gateways

Is there somewhere I can find info on which gateways I am likely to connect to based on my connection (20CN),and their IP addresses?

I can easily find which gateway I am currently on (via PUG, or tracerts).

Also, assuming I have more than one option, is there a way to specify a gateway to connect to on my router (perhaps via static routing)?

There is no way to identify or select which Plusnet gateway you will connect to as it is determined by the BT systems and not Plusnet. There is no direct correlation between IP address and which gateway you will connect on.