If your child is connecting with internet via WiFi, have you tried Virginmedia Web Safe settings ? It is accessible through your account at virginmedia.com.
If it's 3g/4g then it would be good option to search for some apps related to parental control.
Also I would suggest to scan your tablet with some sort of security software, as it seems to be infected in some way. Not sure what tablet it is, however if you search relevant app store (Google Play store for Android, or Apple's App Store for Ipads, etc.) there will be plenty of applications to choose from.