I can see the fun in doing what you have, for the interest of it and to pass the time while you wait! Blimey, I've messed around with spreadsheets and macros for hours, but I personally don't see £50 worth of value here. Certainly not when it gives you nothing more than what your dealer can give you with a weekly phone call.
Oh no, it gives you much more than that. You can compare the everyone's order numbers to their BW (when it is confirmed 4 weeks prior to the build) and also to some basic options including GTI/GTD, doors, colour, transmission, performance pack and dealer (i.e. what place in the dealers allocation it occupies).
This allows some predictions to be made along the lines of which options are causing longer lead times, when orders are likely to be processed based on the order number and dealer allocation, if cars are being built in batches, GTI first? etc etc.... Might even be able to predict which dealers have yet to use their allocations and therefore could let people jump the queue.
Could also tell you other (non GTI specific) things. For example, Deep Black Pearlescent is a highly popular colour choice across the total VW range (and a thousand other facts like this).
I'm not convinced its worth the effort still.