Is personification and metaphor used in 'The Chocolate War'?

Actually, simile and personification are types of
metaphors, as they make comparisons and analogies between things.  So, if you've found a
simile, you've found a type of metaphor.  So, "Jerry walked to the bus like a
sleepwalker" is both simile and, technically,
metaphor.

Here are others:

On
page 24 in my paperback edition:

readability="5">

"Silence fell.  The school was hushed around
them..."

This is
personification, as it is giving human qualities and
actions to inanimate objects, "silence" and "school."

On
page 9:

"A
strange happiness invaded
him."

Here, "happiness" is
personified like a ghost inhabiting a host or an army infiltrating a
territory.

For metaphor, again
on page 9:

readability="5">

"His knees were liquid and his body light as
air."

Here's two similes,
comparing knees to liquid and body weight to air.