Must admit that the fact that it is Australian would put me off in the first place. I don't think I have found one I can really say does anything for me yet.
take it back -Tesco will change it. I've had bad bottles before and they change them or refund no questions asked. I've never had a bad bottle of Hardy's so its probably a one off. It can't be 'corked' because Hardy's don't use real corks they use plastic ones.
Bit damning ubasses, there are some superb Aussie wines - whites from the Margaret River area for example, some lovely S-Blanc and Semillon blends and, for reds, around Adelaide (South Oz). I'm not a Shiraz fan but their Block 64 (blended with Cab-Sauv) was wonderful, reminiscent of a great Bordeaux (Chat. Margaux)........