Some TOCs may not even require you to do a Written Comunication Test now, as it is no longer a compulsory OPC test, and is now up to individual TOCs whether you have to sit it. (It has a very high pass rate apparantly)
I recently sat my assessments with East Midlands Trains, and although I received practice material for the Written Communication Test, and practiced it, we were told on the day that we wouldn't have to sit it.
I wouldn't be surprised if it got dropped entirely soon, or replaced by another test.
Having said that, it's still best to practice it just in-case you have to sit it, especially if you've been told already that you will sit it.
It'll certainly not be the most challenging test you will have to sit in the assessment process.