From Eric Dondero:

The pro-free market, pro-sovereignty UK Independence is arguably the most libertarian-leaning party in the United Kingdom, save of course, the tiny UK Libertarian Party.

Perusing the election results, it appears UKIP polled 3 to 5%. Here's a sampling from one district - West Sunderland (via 538 blog):

Labour 19,615 (53%)
Conservatives 8,157 (22%)
LibDems 6,382 (17%)
BNP 1,913 (3%)
UKIP 1,267 (5%)

It is difficult at this point to discern if they gained any seats in Parliament. The total Minor Party vote, which includes UKIP, rose by a full 1% over 2005 to 6.5%.

(H/t Memeo)