The Apple Watch Series 3 was announced at Apple's September 2017 launch event, and brings with it a few small tweaks like a barometric altimeter and a faster processor, and one big change: optional cellular connectivity.

The Apple Watch 3 is now on sale, but the new cellular options mean buying a Watch is a lot more complicated than it used to be - so here's our guide on where to buy your Watch to get the best deal, including on data plans.

And if you're not sure yet whether the Apple Watch 3 is worth buying or upgrading to, take a look at our review or our full Apple Watch buying guide for a breakdown of all the various models and options.

Before we start, it's worth noting that the cellular version of the Watch not only costs more upfront, it also requires an ongoing £5 per month fee to link it to your phone number and use the cellular functionality - and in the UK it's exclusive to EE, which means it'll only work if you have an iPhone SE or 6 or above on an EE SIM. Another caveat: it does not support roaming, so this additional functionality is available only in your home country.

Read about what you are able to do with a cellular Apple Watch if you leave your iPhone at home here.

Buy from Apple

Naturally, Apple's own store will be the first port of call for most people looking to buy the Apple Watch. You can either visit a physical Apple shop (which we'd recommend for first-time Watch owners purely so that you can compare the 38mm and 42mm models on your own wrist) or head to the online shop.

Buying from Apple online lets you buy either the regular GPS model (from £329) or the GPS + cellular edition (from £399) and you can buy both in a variety of different cases and bands.

Once again, bear in mind that if you buy the cellular edition of the watch from Apple, you'll still need to pay an ongoing £5 monthly fee to EE to link it to your phone number, though the first six months are at least free.

The Apple Store also offers the Nike and Hermès versions of the Watch, and the Apple Watch Edition, which comes in a ceramic case, and prices vary for these models - even going above £1,000 for some.

Finally, Apple naturally also sells a whole range of other straps and accessories for the Watch (including several straps that aren't options when you're buying the Watch itself), so you can further customise it to your liking.

Buy from another retailer

If you don't want to buy directly from Apple, you might find a better price by looking at alternative retailers. For one, you can go straight to Hermès to buy its versions of the watch, though you're unlikely to save any money compared to the Apple store except during a sale. Nike will be a similar option, although at time of writing it lists the Series 3 as Coming Soon.

You can also buy the Apple Watch from most major electronics retailers, which might help you find more competitive prices or offers - especially during big sales events like Black Friday. Bear in mind though that they'll have fewer case and band options than Apple itself.

In the UK, Currys and Argos have the Series 3 for sale, as does John Lewis. Again, please remember that you'll need an EE phone contract to use the extra functionality of the cellular Watch, and will need to pay EE an additional fee, which brings us neatly to the last buying option.

Buy from EE

Finally, if you're specifically looking for the new cellular version of the Apple Watch, you might want to try buying it directly from EE, though it only stocks three variants: Gold Aluminium Case with Pink Sand Sport Band, Stainless Steel Case with Soft White Sport Band, and the Nike+ Space Grey Aluminium Case with Anthracite/Black Nike Sport Band - all in either 38mm or 42mm.

The bigger issue with buying from EE is the available plan - right now the company is only selling it on a £25 per month plan with unlimited data. That gets you the Watch with no upfront charge (or £29.99 for a 42mm size and more for the stainless steel), but costs £600 over the 2-year contract for the cheapest model.

Since the cellular Watch itself starts from £399, you're paying just over £200 simply for the unlimited data, on top of your main phone contract. That means you should be able to get better value by buying the Watch elsewhere and paying EE's £5 monthly surcharge - only £90 over the equivalent 2-year period (with the first six months free), without locking you into a contract.