All of the above (except Babysitters and I only read one Sweet Valley High.) We didn't read Virginia Andrews with adults knowing about it, and our copy of Judy Blume's Forever was confiscated by the headmaster when he found us reading it in the playground.
Biggles, which coincidentally, I reread over the weekend. (Biggles Learns to Fly, anyway, not all 100 or so Biggles books.)
Elyne Mitchell's Silver Brumby series
John Marsden's Tomorrow, When the War Began series. Too recently published to have read it as a child, but good books anyway.
KM Peyton, especially the Ruth Hollis and Pennington books. Some bits may have aged - even in the '80s, I raised an eyebrow at Ruth's brother earning £10 a week and it being a meaningful contribution to the family finances. Other books were set in historical periods anyway.
Mind you, I read the back of the cereal packet or anything else to hand, if I had no books available.