WebForms Project with Mvc Area and Autofac IoC

I have a WebForms project with an Mvc Area.

I have two methods in the Application_Start of the Global.asax.cs to register services with Autofac Dependency Injection respectively;

private void WebFormsContainer()
        {
            var webFormsContainer = new ContainerBuilder();

            webFormsContainer.RegisterAssemblyTypes(typeof(CompanyService).Assembly)
                .Where(s => s.Name.EndsWith("Service"))
                .AsImplementedInterfaces().InstancePerRequest();

            _containerProvider = new ContainerProvider(webFormsContainer.Build());
        }

and also,

private void MvcContainer()
        {
            var builder = new ContainerBuilder();

            builder.RegisterControllers(Assembly.GetExecutingAssembly());

            builder.RegisterAssemblyTypes(typeof(CompanyService).Assembly)
                .Where(s => s.Name.EndsWith("Service"))
                .AsImplementedInterfaces().InstancePerRequest();

            IContainer container = builder.Build();

            DependencyResolver.SetResolver(new AutofacDependencyResolver(container));
        }

The WebForms injection appears to work but when I try the Mvc part of the app I get the error;

No parameterless constructor defined for this object.

Question is how do I set up Autofac for MVC areas in a Webforms app?