As a regular visitor to Australia, I get the distinct impression that Oz wine is cheaper in the UK. I guess production exceeding local sales has to be sold in markets where there's a lot of international competition.
I'd a glass of Rioja recently which I was told cost £3.99 (AUD $6.02). Not great but not dreadful either. We buy a decent St Hallett Shiraz for £9.50 (AUD $14.35) so it's a bit of a shock even in Dan Murphy's. I suspect ours, which is sold as an OB, is St Hallett Blackwell Shiraz ($31.95).