We must distinguish between the literal and figurative meanings. Literally, "as much as £6m" means "the same as £6m". For example, "The amount of soup that Bob had was triple the amount of soup that Sally had" means what is says: Bob had triple the amount of Sally. However, "as much as" is also used in a figurative way in which "as much as £6m" means "Wow! Maybe £6m! Amazing, no?"

Yes, in this context, "as much as" means "up to". So the sentence means: The organisers hope to raise up to £6 million for charity. It implies that £6 million is the maximum amount they aim to raise.

Yes

as much as = up to as much as £6m = up to £6m