Postgraduate accommodation

I’m thinking of applying for postgraduate maths at ICL. However the high prices for accommodation are concerning. Where do people live and where are places I can live and have a commute of say 1-1.5 hours or even getting up to 2 hours?
Also I will be living with my girlfriend so living in a place that isn’t dangerous is fairly important. As I say, I would be prepared to sacrifice the time taken to get to uni for living in a place that isn’t too expensive and isn’t ‘dangerous’