The use and creation of energy has not crept up upon UK. Decisions have been taken to remove abilities to create (coal fired etc) , not invest in alternate methods. Instead import energy from overseas which is not good.
Onshore Wind energy has been shown time and time again to be the cheapest and quickest to install but is obviously subject to weather without a significant storage.
I would have ramped up dramatically on shore wind for short term and transitioned to offshore wind plus nuclear as soon as possible (5-10 years)