Panmure Gordon it has downgraded its rating for insurance group Aviva from 'buy' to 'hold' after the company announced a surprise cut in the dividend on Thursday."The clarification on the dividend may remove an issue that we believe has hindered Aviva's valuation, but we think the market will rightly be disappointed by the cut. We downgrade our recommendation to 'hold'."Investec has lifted its recommendation for temporary power and temperature control group Aggreko from 'hold' to 'buy' following the company's strong 2012 results."Aggreko has delivered on the FY12 numbers and is not changing its guidance for FY13 [...] There have also been some more encouraging signs in current trading year-to-date. On strategy, the group has reconfirmed its confidence in the business model and given clear financial guidance. Today's update is encouraging and we move to 'buy'."UBS has downgraded its rating for industrial manufacturing conglomerate Melrose from 'buy' to 'neutral' one day after the company's full-year results, highlighting issues with the core divisions.While the gas metering division Elster (acquired last year) is performing ahead of expectations, the company said that orders across the wider group suffered in the last two months of the year.BC