How much caffeine is in your high street coffee? - Which?

When it comes to getting your daily caffeine fix, there can be a huge difference when it comes to buying it from the big high street chains. A cappuccino from Costa contains over three and a half times as much caffeine as one from rival chain Starbucks, while a single espresso at Pret has nearly four times as much caffeine as one from Starbucks (and is double the size). What's the biggest factor for you when choosing where to buy your coffee? Does this have an impact on your decision?