What was the Coleophora on Martyn?
On an ornamental Buddleja type bush whose flowers had already gone over, underneath and inter-mingled with a sycamore.
None of which support Coleophora... looking at the case I'm guessing there is Elm around, and a Coleophora serratella case made from Elm will give you the jagged edge yours has but which you don't see on their birch feeding cousins. A long winded way of saying I think you are right!
Yes there is plenty of Elm within 10yds along the cemetery border wall, besides sycamore it is the dominant species of tree. Birch is much further away maybe 50yds.