🚀 go-pugleaf

> I'm moving to Australia for a year in a few weeks. I'll need a mobile
> there as soon as I arrive, but would like to get one that I could then
> continue to use in the UK on my return.

> Since I need one immediately, with no credit background / bank account
> in Oz, I guess a pre-pay system is the way to go.

Possibly. There are other ways that Telstra use, such as the "International
Visitor Service".

This is basically a service where you pay $ 200 by credit card to start up
an account. All your calls and access fees come off this $ 200.

> Can anyone advise me what the best option is:
> 1) What the technical requirements would be for such a dual country
> phone (ie do I need a 'dual-band GSM' unit)?

You need a GSM digital phone. If you want a phone to work on 1-2-1 and
Orange, you need a dual-band phone.

> 2) How I could get a phone that could be used both in the UK and there?

Buy it outright (generally unlocked)

> I see that Optus pre-pay includes a sim-only package - could I put that
> sim into a suitable phone bought in the UK? If so, what would be the

Yes.

> 3) Or should I just buy a pre-pay phone in Australia. Can I get one
> there that I could then use with a new UK pre-pay sim when I return to
> the UK?

Not unless you paid to unlock it.

> 4) Are mobile phones cheaper in Australia or in the UK?

Hard to compare. Especially when you have to consider that handset locking
is a form of subsidising.

> 5) What is the cheapest way to just buy a mobile phone that is not
> committed to any particular network or call payment plan, in the UK or
> in Australia?

Buy an outright phone. That's what outright means. Unlocked, unconnected.