If your shift doesn't exceed 6 hours you're not entitled to any breaks.
If your shift exceeds 6 hours you're entitled to one 20-minute unpaid break. (That's neither cumulative nor progressive. If you work a 15-hour shift you're still only entitled to a single 20-minute break).
Handwashing, etc, prior to consuming food has to be done within that 20-minute period.
Obviously:
(a) an employer can provide longer breaks (and even pay staff during them) if they choose to do so ; and
(b) employers must allow reasonable 'toilet breaks' during working hours.