Have you got it in an exposed east facing location Guest? They need a bit of shelter and do not like the morning sun on their buds when they are frosted, this causes them to drop off.

Camellia buds fall off if they didn't get enough water last August, which is not much use to you now! However make a note on your calender to water the plant (with rainwater) in August this year to avoid the same problem next year.