[nikdaheratik]

You seem to be leaving out the fact that most nuclear plants have a fair amount of downtime as well in order to refuel. While I don't have UK statistics, in the US it's typically 30-40 days per year when they don't run (so 10% of the time or more). So, you would need more than one source to make up for the nuclear plant's downtime just as you would to make up for areas offshore where the wind isn't blowing at top speed.