Argos have a test meter. They're open on Christmas Eve and you can take it back on Boxing Day for a refund.
You do realize that doing such act's leaves the returned item 'used' so this means the item cant be used again. Its sold for cheap to market traders etc.....
I watched a interesting programmer the other night, apparently we would only be paying a 1/3rd of marked up prices for products if people didnt steal stuff. That would be like a triple pay rise¬!
I think there's a difference between taking advantage of a refund scheme voluntarily offered by a retailer, and stealing stuff. If Argos considered they lost more than they gained through their refund policy they'd curtail it (as they do on some products).