From the University of Cambridge comes Underground Mathematics which started in 2012 as the Cambridge Mathematics Education Project (CMEP). The site provides a library of rich resources for age 16+ students with the aim of “Enabling all students to explore the connections that underpin mathematics”. Underground Mathematics was developed by the University of Cambridge, funded by a grant from the UK Department for Education; the resources are now hosted by Nrich. The resources are free for all users; you can read more about the team and their philosophy here.
Underground Maths have given brilliant resource suggestions clearly mapped to the subject content for the new A Level. This is an Excel spreadsheet; for each content statement, Underground Maths have suggested up to three rich resources and up to three Review questions. Each suggestion is hyperlinked to take you directly to the resource on the Underground Mathematics site. Resources that are particularly good at supporting the overarching theme of Mathematical modelling have been highlighted.
These, of course, are suggestions. There are so many outstanding resources on Underground Maths.