Saw white-ish object in the sky at Brompton Cemetery, London - found 2nd object later in my photos that I didn't see earlier.

I was walking my dog in Brompton Cemetery (Earls Court, London, UK) when I heard a helicopter fly by (I see one almost every time I go there because the cemetery is across the street from a police HQ center). When it passed, I noticed something floating in the sky. At first I thought it was something hanging from the tree...like a bug...because it was very still and there was a tree over my head...but then it started moving from left to right very slowly.
I could not tell if it was white or shiny silver....the color seemed to be a mix at times. Could have been changing colors? Or it could have beena reflection due to the sun?
I looked down to grab my phone and when I looked up it was gone. I turned my phone on and looked up again and it was there again but looked like it stalled? It either moved very slowly or was not moving at all. I am not sure if I kept losing sight of it because it was bright outside? Took two photos and then I looked at my phone to switch it to video. When I looked back up it was gone and I didn't see it again.
Well, I thought I saw it a few minutes later but it was way too far away and in the opposite direction so I might have been imaging it? There were tons of commercial planes flying across the park at the time.
I thought the shape was like an oval balloon, but when I zoomed in it kind of looked like something was hanging from it? Reminded me of a jellyfish.
There is a second black/translucent object in the zoomed in photo (taken like 5 seconds after the zoomed out one) - I actually did NOT see that one with my naked eye. I only noticed it when I was reviewing photos later. I thought it could be dirt or dust...but am unsure why it wouldn't have shown up in the zoomed out photo as they were taken right after each other.
The day was hot, cloudless, and had a slight breeze. The sun was really bright and there were no clouds for orientation, so that could have affected my vision. There were also many planes flying by, which is normal for that area. There were a few crows flying around as well.
The objects were much higher than the helicopter, but I am not sure if they were as high as the commercial planes?