We are in the UK too - not that far from London either really. I (the junior member of Team Mum)have no qualms about wandering about on my own at any time of the day or night, whereas Boss Mum isn't happy to do it. I take obvious precautions - telling someone where I am going, when I'll be back etc, having my phone on me and wearing appropriate clothing ie walking boots.
Remember that statistically a woman is LESS likely to have problems from crime in the UK than a man, it is the media attention that any attack on a woman gets that heightens our fears. Look like you know where you are going, that you belong where you are and be vigilant about potential dangers. Failing that, find some other female cachers that don't want to go out alone and go together!