You know if you were telling me you want to go fly in South east asia/south america (just for example) for a new experience, then I would understand where you're coming from.
But to leave one of the best airline in the world and your flag carrier and as a Brithish (I am guessing), to go fly the same short haul in the same part of the world with the same long days for an lcc...then I really can't understand. I would think veeery hard before jumping.