Blimey, that kind of thing stays with you doesn't it. I've followed hundreds of reports over the years and the ones that happen right on your doorstep are the hardest to shake off.
Few questions if you dont mind - how long was it hovering roughly? And was there any sound at all, even a low hum or anything like that? A lot of people miss the sound details because they're focused on what they're seeing.
Also worth jotting everything down now while its fresh, the time, the weather, which direction it drifted off to if it moved. You'd be surprised how much you forget after a couple of days.
Manchester here so not your neck of the woods but keen to hear more. This section of the forum has had a few good treeline sightings posted over the last year, worth having a look through the older threads too.