You can get coco shells to use as mulch but its not advisable if you have dogs, as they like to eat them and it can make them unwell, any way i think you may be after cockle shells, your local golf course may put you on to a suplier as they use them a lot..
Thank you both. It is cockle shell I'm after, not coconut. I tried a google search with mulch seashells but didn't get v far. I'll try your suggestions.