They can supply and install a HUMA regulator... one of the best. I also purchased a Carbon Fiber tank (4500 psi). Scuba refill shops only go to 3500 psi. I purchased a small compressor capable of 6000 psi on ebay.
You know not to surpass the 4500lb limit.. right?
Keep in mind OP, That PCP rifles and pistols have a service life to their tanks. Wierach states ten years and can be re-certified for another 10 after testing. Carbon tanks require retesting either every 3 or 5 year and have a service life of 15 years. Wierach will only service a tank on their guns 20 years max. Even if you never have it full they are going to put a time stamp . So.on it. So use it!
With regards to pressure.. If you buy a gun that requires 3000 psi to fill, you need a way to get 3kpsi into it. If you have an external tank, you will not be able to properly use a 3000 psi divers tank as the there is not differential pressure. The carbon tanks is the only way to go. you can fill X amount of times from 4500 --> 3000 psi before that external will require filling again. Some guns require ( or more aptly, 'will hold') more than 3k. Some go to 3200 and even 3600 PSI. so research your gun and your filling options. Trying to fill a 3,6, or 9 liter cylinder by hand pump will take you forever but youll end up looking like Hulk Hogan. Im not sure if dive shops will go above 3500 psi as Guntech mentioned. and again pros and cons. If you go to a dive shop you will get nice clean dry air pumped into your cylinder. This is good for your gun.
GunTech if im not mistaken you live on VI yes? We have ridiculous humidity here. One of the physical properties of high pressure air is that it does not like to hold moisture. So, when you run your 6k pump you do need to have a water trap in place because as the air is compressed all moisture in suspension will condense and precipitate out of the compressed air. When you go to fill your gun you risk drawing in water... I trust that you do have some sort of separator in place.. If not, its a good idea to put one in. That moisture can get into your gun and mess it up.. Rust and corrosion.... nasty sh**.
BTW that CF cylinder is tested to some 500+bar burst pressure. The 300bar is the typical '80% safety' margin that you would see on most gear in the world regardless of what it is.. this doesn't mean one should overfill a cylinder. kinda like going over max load on your 308.
I hope im not preaching to the choir here.. Nothing worse than being told something you already know. Cheers Gents! Gonna go back to my popcorn for a bit!