For the foreseeable future there is NO alternative to Nuclear energy.
We are just 20 years too late in building new Nuclear plants.
As Mikey says we used to lead the world in nuclear energy.The UK totally abandoned its nuclear program back in the 1970s.
Now we don't even have a training program for nuclear engineering let alone anyone able to build a nuclear power plant. There are only 3 countries in the world that can now build a nuclear power station
Russia, France and China. The Russian design is considered out of date and unsafe so that leaves France and China. Our new station is being built by a French / Chinese consortium.
We abandoned nuclear power due to the very successful
'Nuclear No Thanks' campaine of the 1970s, which in turn was a follow on from the CND campaine of the 1960s. The Nuclear No Thanks campaign was based on the totally false idea that nuclear power stations were a secret way to produce material for nuclear bombs, if fact the technology is completely different .
The governments of the time however were not sufficiently knowledgeable to realise this and gave in to the 'Nuclear No Thanks' campaine by cancelling the entire nuclear program.
We now have a major shortage of generating capacity and a cold winter could see us having power cuts.
Here is the 'Grid Watch' site which shows you from minute to minute how much electricity the UK is using and how much is generated from each source.
http://www.gridwatch.templar.co.uk/
You can see how much Solar power and wind power is being produced at any time. Solar will be at its maximum about now and you can watch as it drops to zero when the Sun sets.