Most Internet Service Providers (ISP's) will have some kind of restrictions on what sites you can browse to. Mostly you probably won't notice, but certainly BT and Virgin Media have some kind of safe browsing. Virgin Media call it 'Web Safe' and it blocks potentially malicious websites and also has a child safe mode if you have children in the house. I believe the 'Web Safe' is turned on by default but not the 'Child Safe' - log in to your VM account, click 'My Apps' from the menu and then 'Web Safe' to look at your current settings and make changes.
But you can also use a service that offers more restrictions and options to help you stay safe, for home or business and they are listed below.
DNS is essentially how your web browser knows what pages to display and the services below monitor and restrict traffic based on certain profiles to help keep you safe. Using a secured DNS provider can really increase the security of your network.
I would certainly recommend either option to protect against malicious web sites.