A lender's maximum tells you what passed its affordability model. Whether you can live with the payment when your fixed rate ends is a separate question, and only you can answer it.
Whether buying beats renting depends on how rent compares with the price of a similar home, and how long you'll stay. Here's how to test both before you commit.
Your deposit gets you the mortgage. Tax, legal work, searches, surveys and moving costs come out of the same savings, and the rules change at the border and at £450,000 and £500,000.