Our international credit rating has been slashed from AAA (the best) to AA (3rd). To put this in context Germany has a AAA rating and the US is AA+. It's not disastrous but it's not good. We've slipped two grades in only a couple of days.
What effect will this have on finances? It'll cost more for the government to borrow money. That means they'll have less money on the day to day things. It's exactly the same as if your mortgage provider put their interest rate up. You'd have less money in your pocket at the end of the week.