I can't speak for the rest of the UK but in Scotland it isn't a case simply of leaving a rod unattended. It's against the law to lay a rod down or use a rod-rest, as that is seen as a set line!
As Bushwhacker has said, not every fish requires an instant strike and some need to be left to run. In fact, I'm pressed to think of any British freshwater fish worth eating that requires an instant strike. Furthermore, I'd be surprised if a spring-loaded hook didn't result in more missed fish than an ordinary barbed and baited hook left for a fish to swallow in its own time.
The greatest concern of a fish is to get the goodies before a bigger boy comes along and nicks his meal... or worse, nicks him and his meal!
As Bushwhacker has said, not every fish requires an instant strike and some need to be left to run. In fact, I'm pressed to think of any British freshwater fish worth eating that requires an instant strike. Furthermore, I'd be surprised if a spring-loaded hook didn't result in more missed fish than an ordinary barbed and baited hook left for a fish to swallow in its own time.
The greatest concern of a fish is to get the goodies before a bigger boy comes along and nicks his meal... or worse, nicks him and his meal!