Start with high-confidence great britain travel books, then narrow by subgenre or adjacent topics.
Where to Go When Great Britain and Ireland
DK, D.K. Publishing
Booked
Richard Kreitner
Before Scotland
Alistair Moffat
London: a Guide for Curious Wanderers
Jack Chesher, Katharine Fraser
Forgotten Churches
Luke Sherlock, Ioana Pioaru
Literary Places
Sarah Baxter, Amy Grimes
Writers' London
Carrie Kania, Alan Oliver
Lonely Planet Scotland 13 13th Ed.
Kay Gillespie, Joseph Reaney
Lonely Planet Experience Ireland 2 2nd Ed.
Isabel Albiston, Neil Arthurs