You can’t download the updates to a USB stick. Each box should be updated automatically with the appropriate version, usually overnight. To check for an update, go into Settings -> Device Management.

These two boxes will be running on different software versions, one from BT, one from TalkTalk, so an update may be available for one, both, or neither.

Why do you think the boxes need updating?

If you’ve checked for an update and not found one, that may simply be because each box is running the latest version of its software. Normally each box would update itself during setup and then check regularly for any new updates.

There’s a list of TalkTalk updates at http://help2.talktalk.co.uk/getting-started/software-update-huawei-youview-box.

For the BT box, see the announcement at https://community.bt.com/t5/YouView-box/UPDATED-25-11-New-software-update-rolling-out-to-YouView-from-BT/td-p/1089512

No. Assuming they’re both in working order, each box will update itself with the firmware it’s looking for – BT version for the BT box, TalkTalk version for the TalkTalk box.

Not that it makes much practical difference. Regardless of which version each box is running, the boxes can’t communicate with each other – they can’t for example share recordings. If you’re on BT’s network and want to subscribe to BT TV services, you’ll need to check with BT about what you can get with each box, whether you can get multiroom, etc. The TalkTalk box won’t be able to handle BT’s multicast channels such as BT Sport for instance.

BT will be more than happy to send you a “free” box provided you sign in blood.