We're an island, surrounded by strong tidal waters, yet we have to get hydro power from Norway. Why the hell can't we, as a nation, get our arses in gear and get to be self sufficient for ourselves. Or even sell any surplus to others.
That's a different sort of Hydro.
The Noggie leccy is mostly Hydro Electric (and Wind). Either water falls as rain/snow into high mountain areas, or you pump it up there using leccy when it's cheap. Then you use the water to drive turbines on the way back down again when you need the leccy at peak time. The UK does have some hydro electricity capacity, mainly in Scotland and North Wales, but it only makes up 2.2% of the UK's generating capacity(1.9GW).
https://en.wikipedia.org/wiki/Hydroelectricity_in_the_United_KingdomTidal is a reliable source, but so far it's worked out far too expensive and environmentally controversial for any government to approve it. You also need to build at least 2 sites at locations where the tides are (roughly) 6 hours apart because tidal doesn't generate much at slack tide.
One of the UK's problems at the moment is that about 25% of our Nuclear power is offline for various reasons.
https://www.edfenergy.com/energy/power-station/daily-statuses. It's mostly due to be back online by the end of October (if nothing else goes wrong) which will add another 2GW of baseload, and reduce the amount of Gas we burn by a similar amount. Winter is also normally windy-er so there should be more offshore energy generated.
You can see all the various sources of UK leccy here :
https://gridwatch.co.uk/Personally I think we need to double our nuclear capacity to supply much more of the base load, and then just use gas to supply the extra if/when the wind isn't blowing. Trouble is it's taken 20 years to get Hinkley Point C built, and Sizewell C isn't exactly storming ahead either so it's not a short term solution.