Barn Owl question

[Columbine]

Thank you for your interesting comments Dogghound and Ross17, I have listened to the calls on the links given and the RSPB web site again and still think it was most likely tawny owls I heard but after your comments, I am listening out to see if I can hear it again to be sure.
My box is not in a building but high up, resting on a big branch, against the trunk of a large ivy clad ash tree which is on the outside of a small belt of trees, it faces outwards and with a clear flight path and doesn't get any disturbance at all. I live in Cumbria and used to see barn owls regularly around my home but rarely now, I imagine like most things nesting will be a little later here than further south. We hear tawny owls a lot, sometimes one sits on our garage roof so from what you and Faz say perhaps the tawny owls have driven the barn owls away or at least are keeping them away. The box is up there now so I think I may as well leave it there and maybe one day something will use it, someone said a kestral might nest in it which would be good.

[Dogghound]

Potentially, Kestrel, stock dove, jackdow and even tawny owl may nest in it. How high from the ground is it about 3 meters is best? is it a purpose build owl box thats quite deep? It is best to use isolated trees for barn owl atleast 100 meters away from wooded areas even more if lots of tawny owl area present. The tree you describe is likely to be of high interest to a tawny owl, they like trees with lots of ivy and often use these as day time roosts.