National Australia Bank is expecting to extract more "synergies", meaning cost savings, from its takeover in late 2009 of Aviva, the Australian wealth management platform business purchased from the firm's UK-based parent.In the course of an interview with Business Spectator, published on Friday, Cameron Clyne, NAB's chief executive, said that, "with regard to Aviva, we are ahead of our business case synergies."In fact we just upgraded our synergies by 29 per cent and our synergy estimates are more aggressive in Aviva than they are in Axa, so I think we're very comfortable that what we're paying [for Axa] is a fair price."Much of the Spectator interview was centred on the strategic rationale behind NAB's bid for the Australian and New Zealand business of Axa Asia Pacific, and he produced this nugget of data in the context of the suggestion that NAB extracted little value from its 2002 takeover of MLC, another wealth manager and life insurance business.NAB agreed to pay $885 million for Aviva and has never clearly spelled out the cost savings and revenue gains that it is budgeting from this business.Meanwhile speculation resurfaced in the media that NAB was considering listing its British banking business operated through Clydesdale Bank on the London Stock Exchange.  The Sunday Times reported the possible listing was part of a broader review of NAB's options for its business in Britain. It appears to be the fall back option if NAB fails to buy the 318 Royal Bank of Scotland branches and associated customer lists that are presently in the market.