There is a justification for having a referendum in London to consider the extension of powers: we had one when we set up the Mayor and the Assembly. If there is to be further substantial devolution then there is certainly a case to be made for a referendum to cement mayoral and Assembly authority over those additional powers.
Another area for London ought to be full fiscal devolution. I welcome the announcement on business rates, but I am afraid that does not go far enough. All property taxes should be devolved. The all-party consensus of the mayoral London Finance Commission report published in 2013 was for a pound-for-pound reduction in revenue support grant as the quid pro quo that London offers back. It remains opaque at best on why the Treasury will not agree not just to business rates but to additional property taxes to London.