Here are some of my favourite maths-y websites:
EDEXCEL: http://www.edexcel.com/Pages/home.aspx
MEI: https://mei.org.uk/index.php
THE TUTORS ASSOCIATION: https://thetutorsassociation.org.uk/
BITPAPER: https://www.bitpaper.io/
GEOGEBRA: https://www.geogebra.org/
WOLFRAM: https://www.wolframalpha.com/examples/mathematics/
AUTOGRAPH: https://completemaths.com/autograph
DESMOS: https://www.desmos.com/
GCSE TUITION: http://www.garethlewismathstuition.co.uk/
HISTORY OF MATHS: https://www.storyofmathematics.com/16th_tartaglia.html
NRICH: https://nrich.maths.org/
ADVANCED MATHS SUPPORT PROGRAMME: https://amsp.org.uk/
LIES, DAMNED LIES AND STATISTICS: https://www.gapminder.org/
TED: https://www.ted.com/talks
CANVA: https://www.canva.com/