IF PROOF were needed of the two-tier performance of the financial services sector then just look to aberdeen asset Management.  While the banking sector was imploding and storing up billions in toxic loans, fund managers were among those keeping the wheels of the financial services industry turning.  aberdeen's long haul back from the brink of its own crisis - the split capital trusts debacle in the early part of this century - is well told. It was a disaster that practically engulfed the company, left its reputation in question and put chief executive Martin Gilbert's future in doubt. Gilbert not only survived but led the firm's recovery, though he has admitted how close aberdeen came to the brink.  after a series of shrewd acquisitions and a strategy of targeting growing asset classes, the firm has been turned into a darling of the fund management sector. It is now the second-biggest independent in Britain behind Schroders and yesterday reported a record first-half profit.  The company's balance sheet is in good shape and cash flow is healthy, allowing it to pay progressive dividends. It is comfortable enough with its growth strategy that Gilbert sees no need for further big acquisitions for the time being.  analysts are encouraged by the figures, particularly the strong performance in stemming of an outflow of funds in fixed income investments which appeared to be the main blot on the accounts.  Gilbert himself accepts that a period of volatility lies ahead, but he seems to be one skipper capable of steering his ship through any troubled waters ahead.  But, ScottishPower still awaits a new leader  It's hard to imagine a FTSE-100 company operating without a chief executive for six months and with no appointment in sight. OK, Standard Life took a long time to replace Sir Sandy Crombie, but he stayed on until his successor was appointed.  ScottishPower, leaderless sinc