Problem with product Price shown on customer side

[Abe98]

Hi, I'm a newbie evaluating Prestashop (v1.7.5.0) and have set up a test shop to try things out. 

I have noticed that although I have configured a product at £40 (VAT excluded) - £48 (VAT included) on the admin [index.php/sell/catalog/products] side, when I look at the same product as a customer - it shows the price as £90 VAT excluded. 

This seems to happen against one of the three products I've set up, the others are working ok (so I suspect I've done an edit on the product that has caused something to go wrong).

The database psxm_product table shows price=40 (consistent with the admin side).

Is this a config issue or a bug?

Please let me know

Thanks

Abe