Now back on topic. 
I've had a better read of this thread now.
The problem is not Plusnet's. The problem is a combination of sites wishing to block IP adresses or IP address ranges, coupled with people who use dynamic IPs wishing to remain anonymous. Roberto's analogy is fair. Here's another. I buy a car, but a guy that mans a bridge with a gate doesn't like my car, so he denys me access over the bridge. The car manufacturer is not to blame for that. If the manufacturer offers another car for a small fee (not their fault, remember), and I accept, I will get access to the bridge. The manufacturer might be able to phone the bridge chappie and ask him to allow me through, but there are no guarantees.
Anonymity online is all very well, and it has its benefits and its drawbacks. You have discovered one of the drawbacks. If this static IP thing is a question of principles, by all means stick to them and put up with the drawbacks.
The solutions are simple:
1) Get a static IP.
2) Change ISP.
The former will not result in any negative issues for you, unless you're planning to use your IP for things that Plusnet would probably prefer you didn't (e.g. Copyright infringement).
Put your hand in you pocket and pay a fiver for a static IP, and pay for the music/software and you* have no problem.
*you - the collective, as I have no idea if you (the OP) are engaging in copyright infringement. Suffice it to say, I doubt a dynamic IP is much of a proof against being tracked down. If it's a case of avoiding security issues of having a public IP which never changes (DDNS, other malware, site bans etc.) I suggest you invest in suitable firewall and anti-virus security, and employ a router with NAT enabled on the IP.
What's a fiver once, versus all that lovely news content? You might save a tenner keeping up to date with current happenings.
(My own guess is that you want a cheap ISP, and anonymity for more freebies, but what do I know? Opinions are based on the evidence provided, coupled with past experiences of others avoiding static IPs. If this is not the case, feel free to put me right.)