It's good that you can visit that place completely free. I have never been to England but that is my dream to go and when I am there I will pass through that place, thanks to you for giving me this information and so I will be a little more about the stories of the world of great people.
Besides museums there's not much free in the UK anymore. Like everywhere else, they want your money if you are to see the sights.
The exhibition is not free, as I said. Churches don't charge entry, but some may to see certain parts. I think you have to pay to see Shakespeare's grave in Stratford.