Hi Ricky,
I’m afraid I haven’t used Monzo in Perth but Matt shared some excellent feedback on using Monzo in Australia earlier in this post which you’ll hopefully find helpful! I think it’s pretty safe to say that you won’t notice that you’re in another country, when it comes to making payments with Monzo. But it’s beta so do take a backup just in case, of course.
The good news is that you can now switch on Magstripe withdrawals temporarily, from the app so you shouldn’t have the same difficulties with ATMs as we did 
You can enable Magstripe withdrawals from Card > Profile > Security. If you’re an Android user, you’ll need to ask support to enable them for now.
You should also check that you’re a verified user, as foreign ATM withdrawals are disabled for unverified users. On iOS you can compare your limits from your Profile in the app with the limits for verified users listed here or if you’re an Android user, message the support team to check - again, this won’t be necessary 