That's right, the interconnectors are all bi-directional. They move electricity where it's needed according to market demand: when the wholesale price is highe

That's right, the interconnectors are all bi-directional. They move electricity where it's needed according to market demand: when the wholesale price is higher in Britain than in (for example) France, the UK imports electricity. When the wholesale price is higher in France, which can happen during winter demand peaks as France has a lot of electric heating, the flow is reversed and the UK exports electricity.