Girls Father: You fucked my daughter!!!, omg WHAT THE FUCK?!!!
Boy: BOBS YOUR UNCLE dick face!
Girls Father: Oh mein GOT!!! im gonna go bustle in the hedgerow.
So "Bob's your uncle" is another way of saying "your success is guaranteed."
You want to go to the stadium? Go straight on until you reach the park, take the first left, and Bob’s your uncle - you're there!
Jack: Go shopping at 10am, get back to play golf, then off to the pub, and a shag later. bobs your uncle