Bit late to this thread but curious - did anyone manage to get footage? I'm over in Staffordshire so obviously wasn't there myself but I've been tracking similar reports across the US for a while now and Lake Tahoe keeps cropping up. There's something about high altitude lakes that seems to attract this sort of activity, whether thats natural plasma phenomena or something else entirely.
What was the movement like? Steady drift, sharp changes in direction, hovering? That's usually what separates the interesting cases from chinese lanterns and the like. The direction of travel matters as well, relative to prevailing wind if anyone thought to check.
Not trying to be the sceptic in the room, genuinely interested. The ancient sites crowd always focuses on land but bodies of water have thier own patterns worth paying attention to.