It is relatively common for MPs to cross the floor and join another party, sometimes with a period as an independent. MPs representing three distinct parties in the House of Commons are much less common.
Richard Acland – Liberals (1935 to 1942), Common Wealth Party (1942 to 1945), Labour (1947 to 1955)
Heidi Allen – Conservatives (2015 to February 2019), Change UK (February to June 2019), Liberal Democrats (October to December 2019)Ind
Carlyon Bellairs – Liberals (1906), Liberal Unionists (1906 to 1910), Conservatives (1915 to 1931)
Luciana Berger – Labour (2010 to February 2019), Change UK (February to June 2019), Liberal Democrats (September to December 2019)Ind
John Cartwright – Labour (1974 to 1981), Social Democrats (1981 to 1988), continuing Social Democrats (1988 to 1990)SDP
Jesse Collings – Liberals (1885 to 1886), Liberal Unionists (1886 to 1912), Conservatives (1912 to 1918)
Robert Finlay – Liberals (1885 to 1886), Liberal Unionists (1886 to 1892, 1895 to 1906, 1910 to 1912), Scottish Unionists (1912 to 1916)
John Horam – Labour (1970 to 1981), Social Democrats (1981 to 1983), Conservatives (1992 to 2010)
Frank Markham – Labour (1929 to 1931), National Labour (1931; 1935 to 1945), Conservatives (1951 to 1964)
Francis Mildmay – Liberals (1885 to 1886), Liberal Unionists (1886 to 1912), Conservatives (1912 to 1922)
Oswald Mosley – Conservatives (1918 to 1920), Labour (1924 to 1931), New Party (1931)
Angela Smith – Labour (2005 to February 2019), Change UK (February to June 2019), Liberal Democrats (September to December 2019)Ind
David Owen – Labour (1977 to 1981), Social Democrats (1981 to 1988), continuing Social Democrats (1988 to 1990)SDP
Jim Sillars – Labour (1970 to 1976), Scottish Labour (1976 to 1979), Scottish National Party (1988 to 1992)
Chuka Umunna – Labour (2010 to February 2019), Change UK (February to June 2019), Liberal Democrats (August to December 2019)
Sarah Wollaston – Conservatives (2010 to February 2019), Change UK (February to June 2019), Liberal Democrats (August to December 2019)
https://en.wikipedia.org/wiki/Records_o ... le_parties