Right so this is exactly the kind of thing I keep saying people should document properly the moment it happens. Did you manage to get a photo or video at all? Even a blurry one is better than nothing.
The treeline detail is interesting to me because there's a cluster of reports from rural Essex and parts of Suffolk where people describe objects that seem to favour woodland edges specifically. Not random locations, actual patterns if you look at enough cases.
What was the light situation like, was it lit up, dark silhouette, making any sound? The hovering bit is key because helicopters and drones have a very distinct behaviour and most people can tell the difference even if they think they cant.
Post back with as much detail as you can remember, the longer you leave it the more your brain starts filling gaps in with stuff it thinks makes sense and then the original memory gets muddied. Seen it happen loads of times on here.