The MPs are certainly subject to the Nolan Principles of Public Life, as are many others including those who work in the courts:
"The Seven Principles of Public Life (also known as the Nolan Principles) apply to anyone who works as a public office-holder. This includes all those who are elected or appointed to public office, nationally and locally, and all people appointed to work in the Civil Service, local government, the police, courts and probation services, non-departmental public bodies (NDPBs), and in the health, education, social and care services. All public office-holders are both servants of the public and stewards of public resources. The principles also apply to all those in other sectors delivering public services. The custodians of the Principles of Public Life are the Ethics and Integrity Commission."
Looks like a report to the Ethics and Integrity Commission would be something to consider. I have no idea if there would be consequences, but they are breaching almost every one of the seven.
https://www.gov.uk/government/publications/the-7-principles-of-public-life/the-7-principles-of-public-life--2