The United Kingdom held a House of Commons election on July 4. This wikipedia article shows that 12 parties won at least one seat. Scroll down quite a ways. One seat is still not decided as of Friday morning.
The English-Welsh Green Party won four seats, up from just one. The only reason this blog post singles out the Green Party is that there is an equivalent party in the United States.
British ballot access is equal and lenient. Candidates for House of Commons get on the ballot with 500 pounds and ten signatures. Great Britain does not suffer from crowded ballots. The typical district has fewer than eight candidates on the ballot.