Cost cutting is down to the suppliers to sort, not tescos.

Aren't price changes usually agreed long in advance?.

This sort of short term demand should never be accepted by tescos. Currency always fluctuates. If tariffs are introduced then obviously they'll negotiate. But currency, not a bloody chance.

As someone said on the Times:

Marmite is produced entirely in the United Kingdom, largely from yeast sludge left over from brewing beer. The value of the pound should therefore have no effect whatsoever on the price of the product.