Yes, you will need a Premium Plan for access. It's free to sign up and start using. This plan also gives you access to other premium products, such as 1:25 000 Scale Colour Raster and OS MasterMap Topography Layer.
This plan will give you up to £1,000 per calendar month of free premium data. This equates to 2 million map views per month - that is 30 million web map tiles! (254x254 pixels). And there are no daily usage limits.
You do not need to enter your card details when you sign up for this plan, but please bear in mind that if you go over the limit of £1,000, there will be a hard stop to your service.
If you decide to input payment details and exceed the free limit then you will start to pay, as per the prices on OS Data Hub.