Further to my earlier post, I can now happily confirm we have a pair of Swallows nesting in their old roost and the Jacks have been going absolutely bollistic chasing them up and down the garden, however they have developed an annoying habit of barking for them to come which we are trying to get them to stop to no avail!!!!  Hopefully we will have chicks soon, and if we are lucky get another two broods after that, we did last year.