Will I get my promo codes back if I cancel a booking made with the codes?

This would depend on the refund type of your booking.

Full refund

1. Any unexpired promo codes will be returned to your account as long as the refund amount is equal to or less than the cancellation fee.
2. Any expired promo codes won't be returned to your account.

Partial/special refund

1. The promo code won't be returned to your account.