Some excellent suggestions thus far, thank you. I think my major concern is people breaking the glass and that I live in rented accomodation so I have to see what I'm allowed or not allowed to do in that respect. The popular idea are the shutters but I'm hesitant about those because if I move I'd like to re-use them but they will be cut to size.
Dominic - I used to have bars on my ground floor windows (before I lived in a flat) and one was always coming loose and one could be twisted, you'll probably test them thoroughly though
.
I'll research the the subject further and look into the shutters anyway just in case. It's something I'm more concerned about now since our clothes horse was stolen and that's just a clothes horse, imagine when things/essentials get restricted and people are more tempted.