The problem is scale. Here is a really good analysis of renewable resources in the UK: http://www.withouthotair.com/
Conclusion: The UK doesn't receive enough sunlight or have enough wind/waves/tidal pools/land to grow food, power cars (of any kind) and meet other energy needs. The UK can never get all of their energy carbon free without nuclear or importing power. The US is in a better place because of solar in the Southwest but we still don't have the technology/infrastructure to transport all of that power.
Conclusion: The UK doesn't receive enough sunlight or have enough wind/waves/tidal pools/land to grow food, power cars (of any kind) and meet other energy needs. The UK can never get all of their energy carbon free without nuclear or importing power. The US is in a better place because of solar in the Southwest but we still don't have the technology/infrastructure to transport all of that power.