Packing strap. Just like spruce root, except that they don't need water and won't rot.
Okay, that sounds like a cop out, but it isn't entirely. My friend Stuart spent time with the Penan in Borneo who traditionally used the most incredibly intricate rattan bindings. On latter trips he found that they were starting to use packing strap, split down in much the same way as you can split down rattan, or spruce root. When he wanted a parang made he had to ask the smiths to use the rattan rather than the new material...they thought that he didn't understand and tried to explain how superior packing strap was compared to the rattan. LOL. Subsequently I used packing strap to braid the lashings to hold my wooden parang sheath together, following the same method that the Penan used, worked very well and still holding after years.
Spruce roots are great for some things, but are just okay for others. It may be that some bindings would be better done with nettle string, or with hazel/willow withies, or willow/lime bark. Roots and withies are a bit more like wire in that they end up stiff, maybe not tight, but durable and able to hold a shape. What sort of trees grow down by the golf course, on the way to Danes Dyke beach? Looks like there are hazel down there and maybe some lime trees. Problem will be permission to harvest. No one much minds if you want to cut nettles, but stripping bark or trimming suckers and shoots is another matter.
Best of luck