Right so this is exactly the kind of thing I love and hate at the same time because the dog reaction is what gets me. Animals don't perform. They don't decide to suddenly be terrified of the garden for no reason, and that detail alone makes me take this seriously.
What did the hovering look like - was it lit up, making any sound, roughly how big compared to the tree line? I've been investigating strange sightings around South Yorkshire for years and the ones where animals react afterwards are always the ones that stick with me.
Also how long did it hover before it moved off? That's usually the detail that separates something genuinely unexplained from a drone or chinese lantern. Would love to hear more before anyone starts jumping to conclusions either way.