Squealing brakes

[kfsn1]

Brakes have got very squeaky the last few days but got no indication of low brake pads. They were recently checked and found to have plenty of pad left. Suspect the noise is coming from NSF wheel. Im confident its the brakes as it only happens when I apply the brakes, plus you can hear the squealing gets quieter and louder as the wheel rotates.

I'm thinking something has got trapped between the pad and disc. Has anyone got the way to remove and replace the back pad so?

Thank you.