UK off-grid folk: how do I go about getting a water wheel/turbine?

I’ve got land with a small river. Seems like if I can use it to generate electric i can probably be totally off grid (already have solar, batteries etc). So how do I go about it?

Assume I’ll need some kind of permission? From who?

Can something just be installed in the river as is? Or do I need to dig a leat or similar?

Is distance from the house an issue? I assume you’d have an inverter near and then a long AC line to the house, buried or something?

Any info greatly appreciated.