The Nissan supplier is piddling compared with other international efforts, so their use of "giga" probably raises some chuckles in international circles. I seriously doubt whether any of the other UK efforts will get off the ground, as there's already oversupply.
The TYPE of battery matters enormously these days, and by the time you ramp, it's very easy to find that there's no market for what you are producing at any price. We've seen this before in our area. Remember the Siemens DRAM factory off the spine road. By the time they were able to produce 1M bit chips in volume, the market had already moved on to 4 Mbit and the factory was a very expensive white elephant. The speed of innovation in batteries at the moment is even faster than that!