I have a recording database FULL of this type of thing (the other one is, I'm guessing you're in the UK so you'll get this, The X Factor keep changing the programme title to things like "The X Factor Six Chair Challenge", "The X Factor Judges Houses" etc. which of course creates a new folder for each variant of "The X Factor").
There is what you might call a workaround for this, but you can specify the folder name in the recording profile - so if you want everything captured by the regex for "Eastenders" to end up in a folder called "Eastenders" then just set the "Directory" field to "Eastenders".
I'm not sure if the filename can include regex but the above will at least stop the creation of folders when episodes are prefixed with "New" or appended with anything other than the programme title :)