john west wrote

My freeview reception from my wall mounted aerial on the rear wall was
fine until a neighbours tree grew all of its leaves.

The aerial height is just a bit below the topmost height of the tree.

Would it help if i *tilted* the aerial *up* to point over the tree,

Nope.

or do transmission signals not work like this?

No they dont. The only viable approach is to
move the aerial so it isn't point thru the trees.

Or kill the neighbours tree.

A better aerial might work still pointing thru the tree.