To get a test before a holiday, then testing a relative abroad and mailing it off from there.
Thanks 
Hi,
I assume you mean Australia? ( AU)
If you order an ancestry kit and get it sent to your address in the UK ( or whatever country outside Australia ) ,
and you then send it here to Australia - the pre paid bag ( to return the sample) , I would think will be for within the UK use and not Aus handled international post.
If purchasing, if it were me, I'd get the kit sent directly from Ancestry to the person out here in Aus , otherwise I would think the pre paid bag in the kit mailed to your address outside Aus is hopeless out here, as the pre paid bag wouldn't be paid for with Aus post to send international to *Ireland (* where our kits are posted to from here in Aus) .
Kind regards
Ps they are pretty quick at posting the kits out, if what you're worried about is the posting times of receiving a kit here in Aus
from Ancestry.
The kits come from within Australia and not from overseas ( by an Ancestry's suppliers within Aus) . It should take no more than two weeks for the person to receive the kit in Aus.
*I Think mine took a week if that ( *obviously this depends where the person is in Aus of course )
Thanks for your reply (and all the other replies). What I meant was I would order a kit to my home in Aus, and take it with me once I can travel to the UK.
I thought it might be a common practice amongst some family historians to have a spare DNA kit or two in their bag for when they're travelling and meeting some family.
Hi,
Ahh I see what you mean ( I think) .
If you buy one here in Aus , get it delivered to to your address here in Australia, and then take it to the UK visiting family - , then you bring the sample back to here Aus to post off?
If so - absolutely no problem at all !!
(as the postage is paid from here in Aus to Ireland , international)
What I am getting at is the pre postage bags in the kits .
If you bought a kit in the UK ( the pre paid bags in the kits) and then sent it from here in Aus to Ireland - Aus post may not accept it, you know what they're like lol.
I don't see you'll have much of a problem with you buying a kit here ( getting it delivered here to your address in Aus, taking it to the UK with you and posting it from the UK )
Kind regards