What's The Power Of Little Parties In The British Political System Today?

As an American I am not completely familiar with British politics BUT... In the U.S. The two party system is far from ideal. There have been several smaller parties crop up over the years and they have all failed to a point. The power of the little parties is that they can force the larger ones to come clean on some issue or another. If a small party is strong enough to muster some support on the ground and create a grass-roots movement then the power MAY shift and the wheels will fall off. (I'm kidding about the wheels but try reading 1984 by Orwell)