The CAA have been fully involved in the EZY assessment in relation to baggage weight, and the increased pax notional weight which has been adopted in order to account for this.
Even if every single square inch of locker space is filled with baggage (i.e. No empty space at all) at typical baggage densities, structural limitations for the overhead lockers are not breached. (There still remains a large margin to account for higher baggage densities if that is indeed the case.)
Properly controlling volume will ensure that on many flights there is unlikely to be much difference in terms of what is taken on board, as many places do not currently monitor weight carefully anyway.