Firstly, I'd like to know if it's possible to administer hostnames on the username.plus.com domain that is allocated to me for my Static IP Address. I expect that I can administer A-Name records for bonafide domains that I register or transfer-in to my PN account, but it would be really useful to have the facility to register hostnames for my default domain.
Next, on the subject of registering and transferring-in domain names. What is the current advice on this? The only article I've found about this still refers to the Force 9 ISP. If I register or pass DNS control of a domain to PN, will that replace the username.plus.com domain associated with my static ip address? Or is this all a bit complex for a domestic account and is someone going to tell me to upgrade to Business Broadband?
To be honest (and this comes up fairly frequently) plusnets dns services aren't known for being great. As I understand it they literally offer the most basic service they can get away with. For some people thats more than enough but for you I don't think it will be.
I don't think you're going to be able to add vanity names to your existing user.plus.com domain. Plusnet are an ISP and any domains / hosting that was once a side offering with their connection packages is not really their core business and they don't have a great deal of interest in it or making it better. The webhosting itself has been shipped out to an external company as plusnet have no interest in it anymore.
They offer a free dns service that is the best i've found so far. You can subscribe to any of their in house domains (or other users) and have vanity domains too (of course that also means you need to have a webhost / mail server / whatever that will allow you to add more than one domain - 000webhost do). You can also manage more than the default A record - cnames, mx, AAAA etc. You can even setup NS records and move (vanity) subdomains out to other nameservers!
You can also move your own domain into their system but unless you become a paid subscriber, it will become shared so their other users can help themselves to a subdomain on your domain. That isn't really a big issue for many folks when you consider the entire thing is free.
I need a new signature... i'm bored of the old one!