On Mon, 21 Jan 2013 20:01:36 +0000, Rick Hughes
wrote:

I bought an item from Machine Mart (magnifier & Fl light) it was
useless, quality of magnifier lens was so poor everything was out of focus.

Took it back the next day ... as I had 'opened the box' would only give
Credit Note.

That's where you went wrong, by accepting that.
Foot down firmly and refuse anything but a refund.