hii, personally i think the best option is splitting your revision time between the old year 10 content and the new year content to begin with. make sure you find out what topics your mocks cover as well so then you can focus revision prior to them. at my school we had time to go over year 10 content in the majority of subjects (some we even finished the content in december). schools will probably also hold extra revision sessions, possibly after school and in the run up to exams, so going to these could be useful if you think it would help going over content with a teacher.