On the topic of same day change / earlier flight for free, EasyJet says:

‘Get an earlier return flight home on the same day at no extra costTransfer onto an earlier flight departing on the same day as your original return flight for free.’

So it is worth pointing out that this is only for the return portion on a return flight booking. This is why I’m currently not doing EasyJet Plus. I have way to many single/one way bookings that this is more effort than it’s worth.