I have a Canon battery grip for my Canon EOS 300D but have no manual to tell me how to use it as the camera is 2nd hand, can i get a manulal or download one from anywhere

I understand there isn't a manual, just a quick how-to guide. Here's some basic use info from a review
http://www.the-digital-picture.com/reviews/canon-bg-e6-battery-grip-review.aspx

The Canon BG-E6 Battery Grip is designed specifically for the Canon EOS 5D Mark II as shown above with a Canon EF 16-35mm f/2.8 L II USM Lens mounted. To get the Canon BG-E6 Battery Grip into the position shown, the LP-E6 Battery is removed from the 5D II and the battery door detaches. The BG-E6 slides up into the battery compartment and locks into place via the tripod socket screw seen on the BG-E6 just below the lens in the above image. The BG-E6 provides its own tripod adapter threads - this functionality is not lost.

The Canon BG-E6 Battery Grip holds two Canon LP-E6 Batteries that deliver double the number of shots or video time from the 5D II. Alternatively, use 6 AA batteries in the included Canon BGM-E6 Battery Magazine shown below.