nut-bar
fruity
kee siao
siao
three stops short of Dagenham
toppy
cracky
up the wall
nuts
bonkers
bats
distraught
off one's dot
batty
crazy as a bedbug
daft
mad as a box of frogs
bananas
berko
bugfuck
plumb crazy
round the twist
wud
funny in the head
unglued
gila
off one's onion
not right in the head
off the beam
nutzoid
off one's trolley
off one's rocker
gone fishing
meshuggener
doolally tap
crackers
hatstand
bughouse
nutso
off one's chump
off one's head
mad as a March hare
out of one's mind
gobaloon
becrazed
one fry short of a Happy Meal
flip out
flip
mad as a fish
insane in the membrane