Hello an additional resource you can use is maths genie. They have full coverage of topics from Grades 9-1. In the case of doing foundation, you will only have to attempt topics from Grades 1-5. I'd advise to try and focus on the topics you find difficult first and do the practice questions associated with each topic until you mastered them. There are also solutions available to the questions for you to mark and see where you went correct and where you went wrong. Then move on to the topics you find easy and attempt questions from them.
There are also really good youtubers like The GCSE maths tutor and Corbett maths as mentioned above if you need help with anything. Maths genie also have videos explaining each topics clearly.
After that pull off as many past papers as you can, they are highly beneficial.
Hope that helps,
Good luck ! 🙂