Unknown flowering tree

Unknown flowering tree

Observation - Unknown flowering tree. Description: Unknown 'flowering' ornamental trees, in St Austell churchyard, Cornwall. Several such trees, 30-40 ft tall, dark green waxy leaves, and large white flowers 2-3 inches across. Never seen them anywhere else, I'm sure they're not native although the leave

Unknown 'flowering' ornamental trees, in St Austell churchyard, Cornwall.
Several such trees, 30-40 ft tall, dark green waxy leaves, and large white flowers 2-3 inches across.
Never seen them anywhere else, I'm sure they're not native although the leaves and bark look a little like Holme Oak.