The Commons Library has just published a useful list with details of when a Member has changed allegiance from one political party to another or decided to sit as an independent MP. Instances of Members losing or resigning a party whip are also noted.
They would like your help: as they say, ‘Due to the difficulties in compiling a comprehensive list of all floor-crossings, whip withdrawals and whip resignations, this list cannot be guaranteed to be definitive. We are always happy to hear of any additions or amendments to the list. Please email firstname.lastname@example.org with any comments.’