How about a boycott of the firms who payed his fees? They must have known it was wrong and I would think they could be considered equally guilty under bribery and corruption legislation.
^This, but legal action not just boycotting. Unless the firms paying the MPs are punished, the sleaze won’t stop. Not defending the bloke, but he won’t be the last individual to accept a nice easy wodge of cash if they think they can get away with it.