London Literary Sites

I think it is obvious, but I will mention the memorial areas in Westminster Abbey anyway.

There's the Dicken's House Museum on Doughty Street; the spot of Chatterton's suicide in Brook Street (though there's nothing to see there); or take the train to Winchester and see Jane Austin's burial place in the cathedral.

There are mentions of literary sites on the Atlas Obscura list for London - don't forget cemeteries (after all, most of your authors are probably in one) :) https://www.atlasobscura.com/things-to-do/london-england/places

My apologies, I forgot the 18th century bit, and only one of my suggestions falls into that (though when I did my history A-Level, the we covered '18th century' up to the end of the Napoleonic Wars, so Austen would creep into that). You could also go to the Old Cheshire Cheese on Fleet Street, where Johnson (and Dickens) drank. It's a Sam Smith's pub though, so avoid the draught bitter.

Since you mentioned Hogarth, there are Hogarth originals in Sir John Soane's Museum. It's a wonderful quirky place to visit.
https://www.soane.org/

Again obvious, but the British Library, unless you're already planning to do research there.

Y'all-thank you so much for your wonderful ideas. I will be looking into all of them!!