.lets say 10-15 years changeover. Yes they'd most likely need to...

.lets say 10-15 years changeover.

Yes they'd most likely need to build one first. Then when that's finished start on another one unless they can wave a wand and magic up numerous teams of nuclear skilled workers.
That's where the smr's are supposed to help being built in a factory but nobody knows as yet how much one will cost.
They better start training or importing nuclear specialists ASAP if they win the next election.