To help understand how the binary system works, you could watch this video on YouTube. It is 14 minutes long and there is some information about Octal that is not required for the GCSE course. I really would recommend watching the start, since it explains how our decimal or denary counting system works and while you already know how – it gives a useful background to understanding binary.
However, if you want to watch the parts just about binary, scrub forward to 7m20s
and to see the clip that explains how hexadecimal works scrub forward to 10m20s.
This video here explains it in a different way.
I am a fan of Bucky (The New Boston) you might prefer to watch and listen to Bucky here.