Many, many of those above - also Elizabeth Enright's Melendy Family series. Plus I had a book by EB White, who wrote Charlotte's Web, but it was another title - will have to check when I'm back home.
Loved KM Peyton - Flambards was good, but preferred the ones about Ruth Hollis (Fly-by-Night etc), Pennington and Prove Yourself a Hero, as well as the various historical ones.
Margaret Mahy - particularly the Changeover.
Someone mentioned GR Kesteven above - the one I reread a few times was the Pale Invaders.
Rosemary Manning - the Green Dragon series
Ruth Manning-Sanders - all her fairy story books, but they have to have the Robin Jacques illustrations.
Roger Lancelyn Green's Tales of the Greek Heroes is mainly responsible for me taking Latin to A-level (Greek wasn't an option.)
Ernest Thomson Seton.
Kipling's Just So Stories, with the great grey green greasy Limpopo river.
I went to the Snowy Mountains when I went to Australia purely because of Elyne Mitchell. I did see wild brumbies, though not a silver one.
One day, I shall go to Prince Edward Island for LM Montgomery and also Rocky Ridge for Laura Ingalls Wilder.
I read loads of Enid Blyton, Diana Wynne Jones, loads of those mentioned above, especially pony and ballet books and adventures. We didn't have a TV, so I read loads (including stuff handed down from parents and grandparents.) And my first job was Saturday girl in the library.