As others have stated, there are several new issue service providers. Generally, new issue service providers charge you more than the face value of the stamps, whereas philatelic bureaus of the issuing entities, normally, do not. However, they may keep track of issues you want and that philatelic bureaus do not send out on subscriptions. The opposite, however, may also be the case.
For some countries, you may find it hard to encounter a philatelic service. I still have not figured out whether Russia's Postal Service has a philatelic service.
The cost of postage may also run up if you receive every new issue from every philatelic bureau you have a subscription with. A new issue service provider may benefit from economies of scale.
Your location states the UK. New issue service provider may save you postage by combining new issues from different issuers and only sending you new issues at fixed times. One thing to consider is that a sending from the USA, Denmark or the Netherlands may cost you more in postage than one from a UK-based service provider.
Also, the UK may levy import duties on such new issue sendings. At present, they will not do so when these originate in another EU country, but this may soon change.
I can add a new issues provider based in the Netherlands to those already mentioned: https://www.postbeeld.com/customer-...ubscriptions
My advice would be to first look at providers in the country where you live. If you only want basic new issues from a few issuing entities, you might prefer to have standing orders with those issuing entities' philatelic services.