How do you revise BIOLOGY SNAB:Edexcel????? Watch
Also the SNAB syllabus is not that different from the normal Edexcel Biology syllabus (I believe) so revise using resources from both. That way even if you learn a little extra you definitely know the content and have an increased understanding of the topics.
Finally there are apps out there you just have to know where to look. Don't necessarily look for subject specific websites or apps. For Example Physics and Maths tutor (.com) don't just do Physics and maths but chemistry and are working on biology as well. Try the app Gojimo if you have an apple product. Although some of it is irrelevant/ slightly more than we need to know more of it is useful, relevant and interesting. It has multiple subjects and could be useful.