I can't speak to conditions in the UK, but in the US, almost no one owns his (or still more occasionally her) own fill station. We almost always get our fills from paintbll fields or paintball stores. There are also some scube shops that offer fills, usually 3K (3000 psi) fills, usually for a lot of money.
The common arrangement here is that tournament players get a day of unlimited air with an entry fee. That is usually $10-$20, with the fee waived for sponsored teams and players.
I know that there are some other paintball related conventions in the UK which I have heard of and find wacky in the extreme, but I would be surprised to learn that most players own their own fill rig. I would think that getting fills through a field you are playing at is the way to go. If you are shooting a DM4 (great choice, by the way), you will likely need air filled at least a couple of times in a day of play.
Is it the case that fields don't supply air in the UK? I thought I heard reference to concession stands over there. If they are feed you burgers but not offering air fills, someone has priorities skewed a tad.
