Lenders should lend responsibly. This means that they should consider whether you can afford the mortgage repayments now & throughout the mortgage term. E.g some lenders offer a discounted rate to start with, but will you be able to afford the repayments when the discount ends?
Recently it has become more common for lenders to make an affordability assessment (rather than a multiple of salary) when calculating how much they will lend you. Each lender has its own method, but generally they all try to calculate your disposable income, taking account of:
1. your total income;
2. any money you owe, such as loans and outstanding credit card balances; and
3. household bills and living expenses.
Be sensible with the level of borrowings and don't over stretch yourself with mortgage payments. After all, there's no point in buying a more expensive house, if you don't have the finances to enjoy living there.