It’s easy enough to do if you just use your noddle (=think).noddlenod‧dle /ˈnɒdl $ ˈnɑːdl/ noun [countable] British English old-fashioned informal 
It’s easy enough to do if you just use your noddle (=think).
EXAMPLES FROM THE CORPUS
- As for splitting the spoils and building separate, well, you must be off your noddle.
COLLOCATIONS FROM THE ENTRY It’s easy enough to do if you just use your noddle (=think).
your head or brain: It’s easy enough to do if you just use your noddle (=think). It’s easy enough to do if you just use your noddle (=think).