This isn't just Marmite, its all Unilever products. Unilever are behaving like most big corporations will, like physchopaths, they are in it for themselves and have no fucks to give for anyone else. Tesco are fighting back as they dont want to take the hit as they know there customers will not like it and they will just go elsewhere.
Dell already price hiked, Now Unilever, lots of other big corporations will follow. You cant lose nearly 20% of the value of your currency and expect everyting to go smoothly!. Things are going to start getting a lot more expensive on the street soon.