It really depends on how much of your monthly take home salary it equates to. From memory, when I earned just over that amount I set my budget for mortgage payments at £1,300 per month, for a mortgage of about £400k at the time. When my salary went up substantially, I increased the DD up to £2,000 to overpay, and that was still comfortable.
On £550k, you'll have repayments closer to £2,000 per month, unless you increase the term to say 30-35 years, which would be fine at age 30. If you are currently taking home about £5,500, £2,000 seems doable, however if you will soon have a DC in childcare at £1,000, perhaps 2 cars on finance total £1,000, plus all bills and food it starts looking a bit tight, as you won't be able to save much. Only you will know your incomings and outgoings to determine what feels right.
I'd work this out by first looking at the monthly payments I'd be comfortable with first, then working that up to the mortgage amount to see if that's enough to get you what you want in the area that you like.