OCR A level Computer Science overview
http://www.ocr.org.uk/qualifications/as-a-level-gce-computer-science-h046-h446-from-2015/
PDF of A level specification
http://www.ocr.org.uk/Images/170844-specification-accredited-a-level-gce-computer-science-h446.pdf
Buy the course book:
https://www.pgonline.co.uk/resources/a-level/ocr/ocr-a-level-textbook/
Computational Thinking Resources from Google Education
“Fun” Reading for Students Starting a Computer Science Related Course by Paul Curzon