I was born in 1975, and I think I read most of these books when I was about 6 to 8 years old - I read a lot as a child though and was more advanced than most!.
I vaguely remember a series of books - they may have got progressively harder through the series!. I do remember lots of pics in them!.
There was a boy or girl, who one day wakes up to find a black cat sat on his window-ledge!. When he/she looks out of his window, he sees a large tree in the garden (I think it had a fence around it) with a broomstick propped against it!. He/she and the cat fly off on the broomstick (which they do regularly each night throughout the series of books) for a variety of adventures!. I am sure that it contained lots of witches, dragons, gryphons etc!.
It has been driving me potty trying to find out what these books were!. At my school, they were in our school library and all our library books had coloured stickers on!. You had to read so many books from each set of colours before you were allowed to get books from the next colour!. It encouraged me to read quickly so that I could get the next books in the series as they were spread throughout the colour ranges!. This could have been that they got harder as you moved on, or it could have been that they just spaced them out that way!.Www@QuestionHome@Com