There are tests taking place with all sorts of storage at the moment, scaleability is often the single greatest problem. Storage for use diurnally, monthly or seasonally will require different techniques.
It's possible that a good part of storage for covering diurnal demand spikes (which will be reduced with the Smart Grid) could be
from personal EV battery storage as well as dedicated domestic batteries such as Tesla's 'Powerwall'. Storage to cover monthly supply deficits would be covered well by tidal lagoons with pumped storage, but given the reluctance of the State to invest for the long term perhaps synthetic fuels made with excess RE are more likely to power us through slack days.
These same fuels could be stored for the many winter days when there's no sun or wind, just the relentless flow of rivers and tides. Geothermal energy also solves so many of these times of shortage, it could be locally sourced or via an interconnected supply network.
We have become so greedy for energy, so wasteful of it and so numerous on this island that moving away from fossil fuels will present challenges for years. A couple of centuries ago Britain needed huge amounts of storage to power dock machinery with one central power source rather than having a steam engine for every crane. William Armstrong of Newcastle developed his hydraulic accumulator, then a weighted version which didn't need a hugely tall tower (useful when building on softer ground) to create a steady water pressure, delivered through a large pipe network.
https://en.wikipedia.org/wiki/Hydraulic_accumulator