What is the percentage of your household income that your core housing and commuting costs comprise?

Current my mortgage, service charge and commuting costs equal 45% of my gross income. I'm trying to work out whether this is reasonable or not. For context, I live in the south east (fairly rural) but work up in London. I suspect my housing % is a bit lower for most London working, but my commuting costs a fair bit higher. Does anybody have any thoughts or figures to share? Thanks!