Harlequins defied their abysmal domestic form to stun La Rochelle 27-17 at Stade Marcel Deflandre and secure home advantage in the Champions Cup round of 16.
Northampton Saints were brought back down to earth after they suffered a 50-28 loss away to Champions Cup holders Bordeaux in a repeat of last season's final.
Bath lost a 26-point lead in an epic south-west derby only to snatch back victory in the most dramatic fashion in the closing seconds to beat Exeter 33-26, before Northampton Saints returned to the top of the Prem table.
Sale emphatically ended a run of four straight Prem Rugby defeats by thumping fellow strugglers Harlequins 43-17 in a bonus-point win at the CorpAcq Stadium in Salford.
Munster bounced back from a disappointing defeat to Bath last week to comprehensively beat Gloucester 31-3 in the Champions Cup at Páirc Uí Chaoimh in Cork.
An astonishing start which saw Bath 28-0 ahead inside 19 minutes proved crucial as the Prem side saw off Munster 40-14 in their Champions Cup opener.
Gloucester beat Harlequins 26-15 at Kingsholm to record their first Prem win of the season at the sixth attempt.
Leicester Tigers eked out a 36-35 win against Sale Sharks as Bath, Harlequins and Exeter all won by big scorelines in Saturday's Gallagher Prem action.