So as far as I can see the RT Practical is not required to be completed.... for PPL skills test purposes
Quite right, the RT Practical is not a JAA PPL requirement.
However, if you want the seperate UK FRTOL then you either do it all in 12 months (which may include the RT written that is a mandatory part of the PPL Training) or, you take advantage of the dispensation for PPL students to do it in extended time frame allowed for the JAA PPL.
Your choice!
As you have to display a level of RT knowledge and competence on the PPL Skill Test, it makes sense to do it all first and take advantage of the dispensation.