Ronald Ridout (23 July 1916 – 5 December 1994)
Ruth Ainsworth (1908–1984)
This series of books were published from the late 60's through the 70's. These were brightly coloured and designed for children to read themselves. The series was published by Purnell.
Sadly this series is now out of print , but here is a list with the book details to get you started on your search for secondhand copies.