Doing that kind of analysis has become very easy and cheap recently.
Some of Britain's smaller IPSs don't like this sort of stuff (e.g. Andrews and Arnold's "implementation" of the government's opt-in child friendly censorship was to have a checkbox on their application page, if you say you want censorship it says you should choose a different ISP...), and so the smart money is on them having not written to ISPs at all. The backbone providers are few, bigger, and much more corporate. No colourful personalities apt to make the government look a fool in a televised hearing. So any letters probably went to the backbone providers although so far as I know none have come forward to say so.
In 2017 the ECJ told the UK government that such mass surveillance is prohibited, and it is also widely rumoured that the government then told the backbone providers to pause the collection.
I don't see the purpose of VPNs as anonymity, and I think many people are making a mistake to see them that way. If anyone really wanted to know who you are, they could file a suit and subpoena PIA. Now you're trusting that PIA really doesn't keep any logs. You have no way of verifying this. Or, if someone has some suspicions about who (and where) you are, they could subpoena their billing information. If someone (particularly a government) really wants to find you, a VPN does little to stop them. You've just introduced a single middleman.
On top of that, you can only take PIA's assurances that they themselves are not tracking you.
I run my own VPN server, hosted in a DO droplet, to get around networks that filter certain ports and websites. That's it. I have considered adding a VM with read-only access to my NAS to the VPN but that's all.
E: NVM, you mean to access your stuff without NAT etc.
Perhaps if you used Bitcoins to pay?
I'd wager that quite a few people would like to pay for a managed VPN service that did the same thing.... however, as once in a while you need to disable your adblocker on some websites, so once in a while you might need to circumvent the blocking on the VPN. I wonder how that might be done.
OpenVPN on Android lets you select apps to bypass the VPN, so I have a second browser on standby if I ever need direct internet access. Or I could use the disable for x minutes feature of pi-hole.
Proper ipv6, shared ipv4 with a port range forwarded for you to use.
Besides that, though, the entire mechanism of Bitcoin is one where all transactions are recorded publicly in perpetuity. It's really the polar opposite of private in that respect. It means that if your identity is ever linked to a particular bitcoin address (as in the not-so-unlikely scenario that the authorities or some other attacker are monitoring bitcoin-for-cash machines), then all transactions linked to that address can be linked to you.
In short, as always, it depends on your threat model. Are you trying to hide the fact that you forwarded sensitive nuclear secrets to overseas actors from a determined U.S. Government investigation? Sorry, you probably can't, at least without a bit of luck. Are you trying to fool Netflix long enough to stream latest season of Arrested Development? Probably doable.
But how does it help you stay anonymous? You are still paying for that server using your CC and they'd have your address and all other info. Unless I can rent the server anonymously, I can't see any point to run my own VPN server. That's why I'm paying a third party, PIA for example, to rent and run that server for me.