Earlier quoted context omitted.
I have similar memories. I remember as kids we used to play in an old castle by the beach, its just open and anyone can go and wander around it. I travel around the UK with my kids and these days everything wants to charge an entry fee, even other castles in similar states of decay/disrepair. Easily my favourite castle https://en.wikipedia.org/wiki/Llansteffan_Castle
There are free to access castle ruins and buildings of a similar age and much older all over the UK, they're hardly in short supply. Maybe you didn't intend it but this comes across as overly pessimistic. It's hardly as if every bit of history in the country has had a fence put round it to charge an entry fee. Not trying to say what you're describing doesn't exist, but the only place I can think of that I've been to…
Only a tiny percentage charge and are treated as proper tourist attractions.