Thanks again to everyone for their kind messages and advice, it really is appreciated!
Just an update, we had the local bobby round tonight to take details for an investigation, I'm not sure anything will come from it, but it's a start. He said they've never had any reports of anything like this happening in our area before.
We're also asking round to see if anyone knows someone local who owns an air rifle, or heard shots, but we live about 5-10mins walk from a pretty rough area so they could have come from farther away.
I mentioned going to the local papers to my Mum, she didn't seem fully sold on the idea although I made it clear I thought she should do it. I think it's mainly that she doesn't want her photo in some whiney article really. We'll see how that goes.
Anyway, I just want to say thanks once more, it's nice to know you can get support from people you don't know so well, as well as those you do!