what pressure is the cylinder rated to? if it's a 232bar then you might have to buy the fill rig and get it converted to a 232 din fitment at a dive shop, approx £20. 300 bar din fits are the paintball norm, but there are defo two types of din fit 300 has a longer thread and a little nipple sticking out, a 232 will screw on but is v unsafe and will leak big time.
hope that all helps, still gonna be cheaper than buyin a cylinder whatever you do