The thousands of consumers planning to snap up a 3G iPhone when they go on sale next month could be hit with bills of thousands of pounds if they download music or programmes overseas, industry insiders warned last week.

Apple and its partner O2 have used the unlimited download facility in much of its marketing for both the first iPhone that hit the shops last November, and the new 3G model, which will be available free on some O2 tariffs.

However, the unlimited data and wi-fi allowances only apply in the UK. Once you start using the device abroad, charges shoot up to £3 for each megabyte (Mb) of data downloaded in the EU and £6 elsewhere in the world.

That means watching the average BBC iPlayer programme, which is about 300Mb in size, would cost £900 if you were in France and £1,800 for someone visiting America.

The iPhone tariffs are not the only ones on which you pay through the nose for overseas downloads. Data downloaded outside the UK costs up to £8 a Mb with Orange’s Dolphin 40 plan, for example, while T-Mobile’s Web and Walk charges £7.50 per Mb whether you are inside or outside the EU.

But owners of iPhones tend to download more data because the large screen makes it easier to watch moving images.

Steve Weller of comparison website Uswitch said: “The iPhone screen is much bigger than that on most mobile handsets. It is also easier to navigate.”

Music downloads are even more common among users as one of the phone’s main selling points is that it doubles up as an MP3 player.

“Just downloading one track would cost you about £9 within the EU and £18 if you are travelling globally,” Weller added. “You would be better off buying a full-price CD from a shop.”

However, Sarah Taylor of O2 said: “Users have to activate data roaming on their iPhone. They then get a message informing them extra charges apply abroad. We are very clear on that.”

But some services such as automatic e-mail updates use data services without asking the user’s permission. The only way to avoid them racking up the bill for your holiday is to disable them before you leave the UK.

If you do need to access the internet through your iPhone while outside the UK, and are likely to be downloading a significant amount of information, the best option is probably to take out a data-roaming add-on for when you require the service.

O2 offers a range of bolt-on options, including a 50Mb package that costs £50 a month.

There are also some catches when downloading information in this country, though.

Analysts say the new O2 deal offers better value than the previous package for those who will use their iPhones for extensive internet browsing in this country thanks to the “unlimited” download policy. But even this is subject to a fair-usage policy.

This means that, although there is no set limit, your connection may be stopped or dramatically slowed if you are deemed to be over-using it.

Taylor said: “A fair-use policy is in place to prevent commercial exploitation or using the iPhone as a modem, which would put everyone else’s experience at risk. So, you may not use your SIM Card or iPhone for the continuous streaming of audio or video content, or file sharing.”

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