Personal Question about Salary!!?

I have been living in London for only a year and would eventually like to buy a house here. What sort of percentage of your salary would you use for mortgage repayments? I know it depends on lifestyle, but when looking at mortgage calculations, it seems that I will never be able to buy!!! Do Londoners scrimp on quality of life to buy a house, do they get a lot of financial help from their families, or do they move to very dirt cheap (and rough) places to get on the property ladder?