Do Australian iPads work in the UK?
To use an Australian iPad in the UK you have to consider three things - phone service, AC power and the App Store.

The iPad sold in Australia uses the same phone frequencies as the UK version so you just need to be able to replace the existing SIM with a UK one - this means that you don't want to buy your iPad from a phone company under contract here in Australia.

AC power is fine, you only need a plug adapter or your family member may already have a USB charger to suit.

Then you get to the App Store. So long as you use an Apple ID registered with a UK address you will get need to use the UK Store, if you use an Apple ID registered in Australia it will have to use the Australian Store.

So, to sum up, if you walk into an Apple store here in Australia and buy an iPad and then give it to someone to use in the UK you will be perfectly OK. Don't set it up till you get there and set it up for them and they will love it.