Bob's your uncle - something that you say after you have explained how to do something, to emphasize that it will be simple and successful. Example - "Yousimplyputon thestainremover,leaveitforanhourandBob'syouruncle,thestain'sgone."
Horses for courses - it is important to choose suitable people for particular activities because everyone has different skills. Example - Ah well,horsesforcourses.Justbecause a plumbercanmendyourwashingmachine, it doesn'tfollowthat he canmendyourcar as well.
Swings and roundabouts - something that you say to describe a situation in which there are as many advantages as there are problems. Example - "If you make more money, you will have to pay more taxes. So, it's swings and roundabouts, really."