Greig Tonks and Joe Ansbro crossed in quick succession to effectively end the game as a contest, before Downey intercepted for a simple try and a valuable bonus point.
Exeter continued their excellent start to the season with a surprise 23-9 win away to Saracens, with Premiership debutant Ryan Davis scoring 15 points.
Davis and Sarries' Alex Goode exchanged penalties before the Chiefs man crossed over before half-time to set them on their way to a first away win of the season as they silenced the home crowd.
Goode slotted two second-half penalties, but despite relentless pressure, Brendan Venter's men could find no way through and Brett Sturgess scored a late break-out try to secure the points for the visitors.
Substitute Lesley Vainikolo's try two minutes from time was just enough to earn Gloucester a tight 19-12 win over Leicester Tigers at Kingsholm.
Bryan Redpath's side led 9-6 after an entertaining 40 minutes of rugby as Nicky Robinson and Billy Twelvetrees traded scores with the boot.
The two men continued to trade penalties in the second half, with the latter levelling matters with just under 20 minutes to go, but Vainikolo smashed through the Leicester line late-on to score, with the help of the video referee.