Hi,
Ive reciently converted my attick into a bedroom and at the moment there is a 1gang 2 way switch in there. I need to get a switch at the bottom of the stairs. What do I do? The switch in the attick has the feed to it. I've put a 3 core twin and earch cable in but don't no how to connect it to the switches. Can anyone help? Email me [email protected] thanks

Go here:
Advice on Three Way Switches and Other Power Sources (http://www.selfhelpandmore.com/switch-outlet/3-way/)
Then click on your wiring setup.

I assume that you are not U.S. I also assume that 3 core twin and earth a is 3 conductor cable with earth wire.

You need two 3-way switches. In U.S, white wire is used for neutral, may be different color for you.