I think the genre of soap opera is sufficiently well-established by now, that most audience simply take a change of actor in their stride.
I am not a regular soap watcher, but I have been, and remember Nick Tildlsey in Coronation Street morphing from a pale sullen youth into a gay icon, and thence into the gurning large-eared gentleman who currently occupies his persona.
The aforementioned 'Ben' seems to have caused difficulty for the casting staff at EastEnders, maybe no young actor wants to be saddled with a character so manifestly unpleasant, it makes his dad 'Phil' look occasionally human - no mean feat in itself.
We'll see if the latest incumbent lasts the course, but given the hugely improbably scenarios that are the lifeblood of any soap's day-to-day occurrences, I am sure that a complete change of a physical individual being unnoticed by absolutely anyone, including blood relatives, is not something that unduly concerns audiences.