Especially for Kam,
You had asked about licenses for collecting crayfish.
I hadn't realized this but you use the same form (fish removal 2) FR2 to apply to the Environment Agency, as I have used for years for other fish removals. You may need to read the fine print to see if this form can be used by non-professional individuals, but I think you will be OK. There is no charge . Basically you are applying to use fishing instruments other than rod and line. I do this for using electric fishing gear for fisheries stock surveys in lakes and rivers, and to remove fish for environmental management purposes. You FIRST need a permit from the holder of the fishing rights. If this is rented, it would be wise to clear all matters through the landowner as often crayfish are not specifically covered in a rental arrangement.
Pacifastacus leniusculus (Signal Crayfish) is the one you want.
Hope this helps.