Richard - I don't know the ins and outs of the Australian visa system (457 means nothing to me for example). However, we have had a LOT of consulting firms in Australia during the last 36 months (including in the last weeks) who've been paying to advertise vacancies on the UK jobs board of Top-Consultant, specifically to attract UK-based consultants to consider emigrating to Australia.
From memory, all have specifically marketed that they'll sponsor visas (otherwise what's the point of advertising to a UK readership on the UK jobs board?!). Pretty sure I recall PwC, Accenture, Deloitte and a whole host of more niche firms advertising for UK talent to move abroad.
I would be surprised therefore if not having a visa was the real issue here, as I don't have the impression that firms there have an issue with securing visas for the right candidates at the moment. I suspect you're either not finding roles where you're an exact enough fit for what they're looking for; or that your internal consultancy experience either isn't regarded in the same light as regular consulting - or possibly is for an organisation they'll not be familiar with and that therefore is being discounted...
So not a definitive answer / solution for you, but wanted to flag that the visa probably isn't what's stopped you from succeeding to date.
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