There is no mechanism for constituents to remove sitting local Councillors, Mayors and London Assembly members other than waiting for the next election. We need a new act of Parliament like the Recall of MPs Act 2015 but which applies to Councillors, Mayors and London Assembly members.
You may be interested in these active petitions
I believe it is only fair that we treat and deal with Local Councillors, Mayors and London Assembly members in the same way as MPs. If these people are convicted of certain offences or suspended from office (as per the Recall of MPs Act) their constituents should have the opportunity removed and replaced by someone who will carry out the wishes of those who voted them in. I believe too many elected representatives are not acting appropriately and think there should be a way for them to be recalled if certain conditions are met.