Thanks so much for your reply. I have just been out to take some more photos. I can't get a very good photo of the bark, as it's covered in moss and ivy (which worries me). However, I do have photos of the bark on branches that were left over from when they were cut. I kept the branches for decoration. I don't know if that'll help in any way? The tree isn't in my garden, it's next door.
I should add that that tree was cut maybe 2-3 years ago, so isn't showing its natural shape. Also, I do remember having little flying seeds coming down off the tree years ago, but I haven't seen any since. Do they only produce seeds certain years? Or has it not produced any because it's been cut. They're meant to get cut every 5 years.
The first photos are from today, looking up. The leaves hang down from the weight. There is also another little baby tree growing out of the side of it, so there is a photo of that. And the last photo will be the bark from the branches that were cut down a couple of years ago.
I appreciate your help so much, as these trees mean a lot to me and I worry they'll be completely cut down soon due to having new neighbours. The existing neighbours have hated the trees for a long time. I don't know how old the trees are, but have been told they were protected and may have been there since before the houses were made. The site was an old school. But I've also been told the protection has now ended, so I'm worried we will lose them.