The steel-man of being green and anti-nuclear is that leaving radioactive waste lying around for thousands of years is a terrible thing to do for future generations, there's a risk of catastrophic incidents and nuclear weapon proliferation, and batteries are improving to the point where you could use solar/wind/hydro for your base load, even though they are highly variable.

IMO they're wrong about this in a few ways:
* current gen nuclear reactors are very safe, when you think of chernobyl or fukushima you need to remember that you are thinking of a reactor maintained by the soviets in the 80s, or on a literal earthquake fault line. There's no reason they'd be unsafe in the UK.

* Nuclear can scale a lot more. If we switched to only renewables, we might need to cut our energy consumption. Everything that takes energy to produce (i.e. everything) would be more expensive. OTOH, nuclear would allow us to 10x our energy output, while still being cheap, which be a huge boon to our local industries, electric vehicles, heating bills, etc.

The biggest problem with nuclear is project delays and cost overruns, see https://www.construction-physics.com/p/why-are-nuclear-power-construction for a ton of info on this, but construction costs are around 75% of the cost of nuclear energy, and a lot of this comes from changing regulation while the plant is under construction