Many internet service providers (ISPs) provide parental control software - most of which includes content filters which can block offensive content.The four big ISPs - BT, Sky, Virgin Media and TalkTalk - provide it free of charge (as part of their package), and give new customers a prompt so that they have to make a decision as to whether they want to use it or not.
UK mobile operators also provide free parental control software. Some of this is set up by default, but if you are not sure then contact your mobile operator and ask them.
There are parental controls available on a wide range of devices. Whether your child is using a games console, a tablet or a smartphone, it is likely that there are controls available for parents to use.