John McDonnell , Jezza's shadow chancelllor likes going on anti austerity protest marches read about it on link below.
Here is a good picture from the march.
Going on these marches obviously makes John & Jezza feel good about themselves but if they really want rid of Cameron all they have to do is point out to their followers that if they don't vote for Remain in the Referendum Cameron will lose and as Ken Clarke says he will be gone 5 minutes later. Will this upset the Tories? Not at all. Most of their grassroots hate Cameron whom they rightly see as a crypto LibDem. Then the Tories elect a new leader, probably Gove, if they are smart, and he won't want Osborne with all his baggage as Chancellor. He might get someone who has lived and worked at a real job like Liam Fox.
Its great! Everyone wins the country, Labour and the Tories. Who loses? Well only the LibDems and who gives a stuff about them and Nick wont get his lucrative EU commissioners job. Double rejoicing!