Presumably you now have no leaves so you can't post a photograph of these 'white blobs'. Could have been anything from scale insect to woolly aphid to whitefly to mildew, can't say without more info. How long have you had the tree and is it planted in the ground? What part of the country are you in?

The blobs looked like polystyrene, were quite small and very white and only seemed to be one per leaf. Have had tree for two years and is planted in the ground. Live in Essex. Also, seem to have new leaf growth at the end of branches, so any suggestions how to protect it?

Likelihood is it was badly affected by drought earlier on - I know Essex was as dry as we were in West London, so if you weren't watering, that accounts for the leaf loss. Your description of the white dots still doesn't signal any specific problem to me.

Ok thanks.

Re the white dots, I'm now wondering if they were galls - but can't confirm one way or the other without a pic. Even if they were, that wouldn't cause leaf drop.