is very different. here you have different types of water at different prices and here you have one load of water, a still bottle of water perhaps if you like; it’s all bought on the same day, you get your fixed price, that wont change. it’s not being topped up at all. when you get at the end of your deal, the whole thing disappears and you can choose to sit with an empty tank or get a new fixed deal or leap back to the variable pot.
now why somebody would want to go to the variable route, main reason for that to be honest is that you don’t know 