Those of you not wanting to fork out extra for 4G will want to take a look at Three's offering, which won't charge you any more than it does for 3G making it a seriously attractive offer.

While data bundles are not clear at this time, it does look like anyone on an all you can eat data tariff will continue to stay unlimited - take that O2, Vodafone and EE!

Best 4G handsets

The most important part of your new contract will be your new smartphone (assuming you haven't already purchased a 4G-ready device). Possibly the biggest phone for any network right now is the iPhone 5.

As you may have heard, O2's 800MHz 4G band isn't supported by the Apple device, so to make the most of your iPhone's mobile web, you will need to choose a different network. That said, we would highly expect the next iPhone iteration - iPhone 6 anyone? - to be available on O2 from the outset.

Don't go thinking that Vodafone will be able to offer Apple's iPhone 5 on 4G either though, since that network's running the 2.6GHz and 800MHz bands... neither of which are supported by Apple's latest handset.

What about the other 4G-ready phones? O2, alongside both EE and Vodafone, will be carrying the 5 star rated HTC One plus the Samsung Galaxy S4, Galaxy S4 Mini, Sony Xperia Z, BlackBerry Z10, Q10, Nokia Lumia 925 and Lumia 820.

The smaller HTC One Mini and Xperia SP is available on bith EE and O2, while the BlackBerry Q5 is with Vodafone and EE.

EE currently has 15 different 4G devices, including the network-exclusive Huawei Ascend P1 LTE. O2 will be offering 13 different devices, and so too will Vodafone which also has 13 different handsets.

Three hasn't announced which handsets its 4G service will work with, but it currently has 11 enabled handsets in its store including the HTC One, Galaxy S4, iPhone 5, Xperia Z and Lumia 925.

  • For a full rundown of the best 4G phones out at the moment, head over to our in-depth feature on this very subject.

Best 4G deals

Also important to your new plan is what else your chosen network can offer you. Whether it's a free cinema ticket or free gifts from the high street, each network has its own goodies to try to tempt you across.

EE's headlines offers include EE Wednesdays, a continuation of Orange Wednesdays, with a free cinema ticket available mid-week for all EE customers, as well as the uninspiring EE Film app, allowing you to rent films.

Being the longest serving 4G network, EE is also able to offer double speed 4G, with 12 UK cities having a theoretical 150Mbps top speed. Probably more interestingly, EE will also be bringing shared plans, so you can access 4G on multiple devices.

EE also offers a few other services including Cash on Tap, a NFC payment app which comes with a free £10 of credit, as well as free access to BT's and Virgin Media's London Underground Wi-Fi hotspots.

There are also reports that the big red Vodafone network will be offering shared plans at some stage. Vodafone also offers a Sure Signal box, plugging into your router to offer mobile signal at home. Elsewhere, Vodafone VIP is available to customers, offering tickets to Vodafone-sponsored events.

More importantly, Vodafone is offering 3 months unlimited data, as well as offering to buy customers out of their contracts, should they upgrade. Also being bundled in with 4G plans is your choice of either a Spotify Premium or Sky Sports Mobile TV subscription.

O2 has long had Priority moments, offering up high street discounts from money off chocolate to cheaper flights or 2 for 1 entry at a theme park. O2 also offers Priority tickets, offering up tickets up to 48 hours before general release, and Priority sports gaining access to a variety of sports-based offers.

O2 also offers TU Go, an app that enables you to use your O2 number to make calls and send texts via Wi-Fi from not only your phone, but also your tablet and laptop - which even includes the London Underground.

With Three determined to provide 4G at no extra cost to customers it's unlikely that it will through in any free services alongside it.