So I have some progress on my initial query above which may close this out for any who find themselves in a similar situation in the future.
As Vikram eluded to in a previous post, “area” and inherently the units they are in does come in to the equation when considering wattage. So a conversion in dynamo to account for sq ft rather than sq m is needed to produce the correct wattage results which is doable using the “Convert between units” node.
The problems that I thought I was having with this node producing erroneous results was due to the fact that I was validating the wattage values being pushed back in to Revit using a calculated value in a schedule (visually comparing the two). After some digging I realised that my Dynamo results were in fact much more accurate as the calculated values used rounded values from the schedule itself to produce total wattage whereas Dynamo extracted actual area values to many decimal places of precision.
All part of the process of learning to use a new tool, cheers!