The book I am thinking about would have been published before 1968 I believe because i read it when I was about eight or nine in 1967. I live in England. I believe i borrowed it from the library or the school library.
The book was about a group of children staying in an old Abbot’s house or at least close to an old monastery. Virtually all I can remember of the plot was the finding of an old map in a settle in the house, which led them to find treasure in the monastery garden. I seem to remember the treasure was actually from the church and it was important for some reason that it had been found.
I know it is very little to go on!