These leaf blotches don't appear to be a kind of rust/fungi....are insects the cause?
No identification made yet.
No interactions present.
There are a number of different leaf spot diseases of Acer but I am not sure this is one of them. You could try putting the observation into the invertebrate group to see if anyone there can come up with an id incase its an insect and if they deny responsibility as well then perhaps bring it back to fungi.
Thanks, Mike - I've altered the info to 'invertebrates, and hope to get a response.
Lat/Lng: 50.6635, -1.4066
OS grid ref: SZ420850