Here in the U.S., we call the moulding you're attaching
mop board... it's the trim board that finishes the bottom of the wall where it joins the flooring, no? If the wall to which it will be nailed is drywall then the nails will be finishing nails and probable 6d in size. The "d" is called "penny" here. Here's a good description and picture of what I'm trying to describe:
http://www.sizes.com/tools/nails_finish.htm ...
Drive it so that only about 1/4 inch remains... don't drive it with the hammer all the way in. You'll notice a small "dimple" on the head of the nail. This is to hold the nail setter or punch, which is a tool about 4 or 5 inches long with a point on one end that fits into the dimple and a head to be struck with your hammer on the other. Finish driving the nail to just below the surface of the moulding. I'd drive them about every 10 to 12 inches apart and drive them near the bottom of the board, not the top so as to nail into the base plate behind the drywall... The small hole can then be filled with a wood putty matching the color of the board. All the items are available from any good DIY store. On larger jobs, such as remodeling or new construction an air driven nail gun is used for efficiency... the nails are in a coil fitted inside the gun...