Britons will not be allowed to vote for The Apolitical Party, the Yorkshire Socialist Alliance, or The U Party after the political parties' attempts to register these names were rejected.

This is the full list of rejected political party names.

There are some silly ones.
The Electoral Commission, which regulates the use of political party names, blocked the names in an attempt to minimise confusion with other existing parties.
A list of names obtained by BuzzFeed shows that the Commission has in total rejected attempts to register 25 political party names since 2010.
The list also reveals that the Commission rejected the registration of “An Independence Party” on the basis that the name would be too similar to UKIP’s, despite allowing the registration of “An Independence From Europe”.
An Independence From Europe took 235,000 votes in the European Parliament elections 2014, and has been accused of dishonestly taking votes intended for UKIP.
UKIP itself also appears to have tried to re-register as “United Kingdom Independence Party (UKIP)” in order to maximise the name recognition of its acronym. The Commission judged this name to be too long.
Most of the names were rejected because they were too similar to the name of an existing party, many of which were minor parties with zero support.