The UK has had complete political unity on building new nuclear power since 2006. That tells you the timelines.

For Hinkley Point C with the latest estimate being the first reactor online (not commercially operational) in 2030 that gives a "planning to operation" time of 24 years.

For Sizewell C EDF are refusing to take on any semblence of a fixed price contract and they are instead going with a guaranteed profit pay as you go model. Where ratepayers handout enormous sums today to hopefully get something in return in the 2040s.