A couple of things about exchange rates. Firstly, always make sure you know what the rate is between what you’re spending and what’s in your bank account.
Secondly, always assume it’s worse than that. If the rate is, let’s say, 2.7 to the pound (or your native currency), do your calculations based on 2.5 – not 3, even though the maths would be easier. This means when you get your bank or credit card statement you’ll be in for a pleasant surprise! And you’re less likely to overspend.