If you're a professional they will allow more as you're deemed lower risk and a proportion of annual increases and bonuses are taken into account.
You should talk to a broker who will take your earnings, net disposable income and whether or not you have dependents into account and will tell you how much you're eligible to get.
From that you can work out if you can afford the repayments without your lifestyle changing too much.
its a swing from 35% to 50% depending on your income and occupation using a 2% stress test, also this is for total borrowings ie car/personal loans as well
(if applicable)