If the utterly exhausting heat of the British summer so far hasn't gotten to you yet, then there's a fair chance that as summer rolls around, you're already planning a nice little holiday getaway to a country that's even hotter (seriously, why?)

The trouble is, the last thing you want when you've forked out for flights, a holiday wardrobe, a nice inflatable avocado for the pool, and a fair few cocktails is a massive phone bill the moment you get home. And we've all been there, caught out by an emergency phone call or a couple of moments on data, away from the wi-fi.

But not to worry – if you're an O2 customer, you can roam with up to 25GB of data in the EU at no extra cost. Which is more than most of us need for a week or two on our jollies.

Wow, 25GB of roaming in the EU. What's the catch?

There's no catch. If you're with O2, roaming within the Europe Zone is included as part of your tariff – so you can use up to 25GB of data, and all your minutes and text allowance just like you would at home.

If your current data allowance is over 25GB, you'll still be subject to the 25GB Roaming Limit, which is totally free. O2 will even send you a text to remind you if you're nearing the limit.

You can go over the 25GB, no problem – but you'll be charged £3.50 per GB. And if your UK allowance is under 25GB, this limit will also apply in the Europe Zone.

Find out which countries are covered in the Europe Zone here.

Brilliant. But what if I want to go further afield than Europe?

It's not a problem, it just works a little differently. O2 customers can take advantage of the O2 Travel Inclusive Bolt On, which offers inclusive data across 27 non-EU destinations.

Find out which countries are in the Inclusive Zone and covered by the O2 Travel Inclusive Bolt On.

For other destinations outside of the Inclusive Zone, the full O2 Travel Bolt On allows you to pay a fixed daily rate of £6 while you're away.

This fixed rate covers sending unlimited texts, making unlimited calls, and using unlimited data. Which is an absolute blinder of a deal (although data speeds might vary.) You'll only be charged for the days you use the data, and like Cinderella, the clock resets at midnight (local time.)

That's awesome. How do I get the Full Travel Inclusive Bolt On?

If you're staying in the EU, there's nothing you have to do – just make sure you've turned on roaming on your device.

If you're going to one of the 27 countries in the Inclusive Zone, you should be able to see the O2 Travel Inclusive Bolt On activated in your My O2 app.

For further afield than the Inclusive Zone, you can get the O2 Travel Bolt On by texting O2TRAVEL to 23336 to activate O2 Travel. It can take up to 24 hours to be applied to your account, so make sure you give yourself plenty of time before you get on the plan. Forget to activate it, you'll be charged standard roaming rates.

What if I'm not on O2? Can I switch?

Of course. That's where we come in, with our top deals for the summer on O2, on the shiniest new phones from your fave brands.