My first instinct would be to say anything that allows water to pass through but retains very little such as a fine mesh or fiberglass screening. I know this doesn't sound too attractive so I'm curious to see what others would use. Maybe the same type of fabric they make those biodegradable fabric pots from?

Sorry I couldn't help more, I don't do many arrangement type things, but I saw this and didn't want your post to get lost.

You can also use sphagnum moss, often sold in dried sheets at better craft stores and garden centers. My nursery usually makes a quantity of succulent/sedum wreaths and kissing balls for sale and that's what they use. But coir/coco fiber or burlap (hessian) will work also - both should allow the very free passage of water. And I agree, the mix is what is important.

Moss lined succulent baskets.

Any pour thru liner will deteriorate so make plans to reline baskets every 1-3 years depending on what you use. I use coco liners and burlap and burlap has lasted longer. Consider watering a little less

Thanks for your opinions! I know the soil/mix is the most important part and am glad to hear that the burlap should work fine. I might experiment with the sphagnum moss also. Some of the baskets are quite small so the coco fibre would be too thick for those I think but it might be ok for the larger ones. Will post some photos up in the near future once i've experimented a little :)

Thought i'd take a photo just to give you an idea of how small the small baskets are :)

Those are quite small, I think if it was me I'd try burlap or landscape cloth, landscape cloth would last longer. In larger baskets I would definitely use coco fibre, it drains well and lasts a long time. my coco fibre basket is still looking good, this picture was taken 3 years ago a few months after it was planted up, don't have a recent picture but it has filled in and is chockablock full and spilling over the sides, coco mat is standing up well.

Just wanted to add, the coco liner is different than coco peat - it is made of longer 'strands' and I think it drains very well in hanging baskets. I agree that for small ones it may be bit thick, but still would consider it - depending on the root system of plants. But the plants in small baskets may have to be re-potted soon anyway if they start growing well - so even then it may be enough mix for a season or maybe two.

Very nice hanging basket - so colorful, aftermidnight...Rina