Yes you always keep creditors informed of your current residential address. This is to avoid a CCJ as they used your last UK address for the Court claim. Yes you will receive letters for awhile, but not much they can do.
From previous cases reported to this site, Australian Courts do not appear to be that helpful in applying foreign debts. It is probably possible for a determined creditor to enforce the debt in Australia. But for a debt of that amount it is very unlikely, as economically it is not viable.
Most likely the debt will be sold to debt buyers, but not until the original creditor have written it off as a loss against tax. So you could be waiting years for the debt buyers to chase for payment.
I moved permanently to Australia 10 months ago and left a credit card bill of around £2500 that I was paying upto the point where my temp contract in Australia came to an end, now they've sold the debt to a debt collector that's now saying I have 26 days before they get their legal team to seek a ccj, they don't know I live in Australia now, should I tell them I live in Australia to block the CCJ? what are the consequencesof them knowing my address?
Don't touch them owe me £500 since January 2019 make excuse after excuse. Seem they always have software problems sending money out. Keep saying they will call back or email nothing been chasing it now for 6 mths the phone staff always have the same banter we will chase it up and get back to you then nothing!