One of the new features in iOS 4.3 is Personal Hotspot, a feature that replaces the tethering function that debuted in iOS 3. We've caught up with the UK networks to find out what we can expect to pay for the service, especially in the light of the fact that this Personal Hotspot service could equip a WiFi only iPad with 3G functionality, saving you £100. 

See: How to make an iPhone hotspot: Turn your iPhone into a personal Wifi hotspot

Tethering was limited – it only worked over Bluetooth or USB and supported a single connected device – and it cost around £15 per month, on top of your monthly tariff. 

Personal Hotspot lets you share your iPhone's 3G data connection with other devices via WiFi, USB, or Bluetooth. (Note that iPhone 3GS users can only share network connections via Bluetooth and USB, and not WiFi.)

UK mobile networks are still finalising the details of their plans, but we can confirm the following.

Three says that if you're on The One Plan with Three tethering is included, so there's no extra cost for Personal Hotspot. Three told us: "On The One Plan Three gives customers all-you-eat-data, which includes allowing them to use their phone as a modem for tethering, so customers on The One Plan are free to use the Personal Hotspot feature as they like without incurring any additional charges. Customers on other tariffs or on PAYG will have the data use from the Personal Hotspot feature deducted from their allowance as they would any other data use. The best value option in this case is to buy a mobile internet add on.

O2 says is soon to offer new tariffs, but told us that for now its customers can get an Internet Tethering Bolt On for £7.50 a month (500GB). O2 told us: "We’ll be offering some new tariffs in the near future that include tethering as part of their data allowance, however for the moment O2 customers looking to tether need an Internet Tethering Bolt On which costs £7.50 a month and gives 500MB of data access."

T-Mobile offers Pay Monthly customers a Mobile Broadband Booster for £5.10 a month (1GB). T-Mobile told us: "T-Mobile users who wish to take advantage of iPhone 4's Personal Hotspot functionality have two options. If they are a Pay Monthly customer they can add a Mobile Broadband Booster to their monthly tariff. This will cost £5.10 per month for those who already have Internet on Your Phone included in their monthly tariff (which will account for the vast majority of iPhone users), or £10.21 for those who do not. This will entitle the customer to a Fair Usage Policy Amount of 1 GB per month. Pay as you go customers, and Pay Monthly customers who do not subscribe to a Mobile Broadband Booster, will be charged at our normal pay as you go rates for mobile broadband usage. These are: £2/day (Fair Usage Policy Amount: 250 MB), £7/week (Fair Usage Policy Amount: 500 MB), £15/month (Fair Usage Policy Amount: 1 GB)"

Orange says it it will offer tethering for £5 a month (500MB). The network told us: "To enable personal hotspots as part of the new iOS 4.3 update feature, customers need to have a tethering option on their account. Tethering bundles are available for £5 per month for 500MB data, and customers must be on an iPhone specific tariff for this. It is a monthly bundle that can be cancelled at any time, subject to 30 days notice."

Vodafone will offers 500MB for £5. The company states on its website: "Tethering is charged separately from the 1GB of mobile internet use that you get as part of your pay monthly price plan. As soon as you tether your laptop or netbook to the internet, you'll pay £5 for 500MB that lasts for 30 days. Use more than 500MB in that time and you'll pay £5 for each extra 500MB." Read more here: iPhone Tethering and Personal Hotspot charging