Bearing in mind this is for international catridges but which brand is the best and which is the best value for ink?

Diamine
Herbin
Private Reserve
Visconti
Waterman

Waterman, Herbin, Diamine, PR, Visconti would be my ordered preference. Waterman is the original maker, by the way.

Really the question has no answer without you saying what you want out of an ink. I can't stand Waterman's - their ink just doesn't do it for me - but for you it might be the best thing since sliced bread. They have different colours, different amounts of shading, work better in different pens etc etc.

In terms of price I suspect that they go diamine, herbin, Private reserve, waterman, visconti - but you can check on loads of web sites.

Cheers

As Will says, it depends on what you're looking for. Waterman is the safest for your pens. I suspect that Herbin is a close second to Waterman, but I think Richard Binder may have issues with that. I've never had any trouble with Diamine in vintage or modern pens, and they do have a nice color range. If you are looking for really intense, saturated color, try Private Reserve. Their ink seems to like more types of pens than Noodlers.

Noodler's also does not come in cartridges.

If you're looking for value, refilling cartridges is the way to go. Those little suckers are way more expensive than a bottle of ink and a syringe. It's not ideal for everyone's situation, but you'd really have to be on the go with room for only one pen to have it not work for you at least some of the time.

Waterman