Sorry I studied castles from 16-18 so I have major autism for them. Yes I do want an historically accurate setting for King Arthur, with the magic stuff on top. I want to suspend disbelief and think that maybe, just maybe, it actually happened that way. It's like if Jon Snow ploughed a Motorbike into the White Walkers in Game of Thrones, it doesn't belong.
I'm sorry to break this to you but we have shit for castles, most of them got blown up with cannons in the English Civil War or rebuilt into something else. You'll be lucky to see a raised mound of dirt at the location of a castle, otherwise bar a few exceptions it's ruins. We do still have ye olde cathedral towns with epic cathedrals and ye olde universities though.
Even fucking Hogwarts, the pinnacle of British movie castles was mostly cathedrals and university buildings. Pyke and Winterfell in Game of Thrones are CGI'ed Northern Ireland ruins. The Merlin castle was in France!