Downing struck his sixth goal of the campaign after 25 minutes and fit-again Heskey wrapped up the points 10 minutes from time before a late consolation from Paul Scharner.
Victory ended a run of three successive Barclays Premier League defeats and eased Villa's relegation fears.
It was also a boost for Houllier, who had come in for criticism from Villa fans for his behaviour when returning to Liverpool for Monday's clash.
He was warmly applauded by the Holte End when making his way to the dug-out and then saw Downing and Heskey ensure Villa remain unbeaten against Albion since 1985.
Source: PA
Source: PA