For that reason, from time-to-time, there will be a Member of Parliament who is an Independent - that is, independent from any political party and in no way beholden to the Party Whip systems. Independent MPs are quite rare these days but, in the 20th century, there were quite a few - see the lists in this Wikipedia entry and also see The Guardian - Other Famous Independent Parliamentary Candidates. One notable recent independent MP was the broadcaster Martin Bell - elected as an Independent MP for Tatton (in Cheshire) from 1997 to 2001 having stood on an anti-corruption platform against the sitting Tory MP, Neil Hamilton.
Some categories of individual are disqualified under
the House of Commons (Disqualification) Act 1975 from becoming an MP. These include certain holders of judicial offices such as Judges of the High Court. A District Judge (Magistrates' Courts) is disqualified but Justices of the Peace may stand for Parliament though, in their case, guidance issued in March 2015 applies. The guidance reminds those magistrates who are also prospective candidates that, during an election campaign, they may not sit as a magistrate in the same local justice area as the constituency concerned until the result of the election is known. If actually elected, the magistrate must seek reassignment to a different local justice area or stand down from the active list.
The House of Lords Act 1999 reformed the ancient link between hereditary peers and the House of Lords. Today, under a compromise arrangement, only 92 hereditary peers may sit in the Lords. Any hereditary peer who is not one of the 92 is entitled to stand for election as a Member of the House of Commons.
Interestingly, the SNP is urging that defeated or retired MPs are not retained in politics by their elevation to the House of Lords. The Lords is already a large body with around 790 eligible to take part in the work of the House - see here. In the early years of the 2010 to 15 Parliament, David Cameron created well over 100 new peers. Attempts to reform the House of Lords have usually tended to fail though there will doubtless be further attempts depending on the make up of the next government. Previous Post 20th May 2011 - Plantagenet Palliser - after 100 years, will Lords reform arrive?