I've just played around with the configurator to see how various figures work out.
The car with extras cost £29,695 retail. I'm getting it cheaper through DTD but the deposit and their discount is too much for the VW configurator to use so I'll stick with the above figure.
£6k down....36 months....10k miles....£359.12 month.....GFV £14,580.90....paid over 3yrs....£12,928.32...plus GFV = £27,509.22
£6k down....36 months.....5K miles.....£324.62 month.....GFV £15,898.50....paid over 3 yrs....£11,686.32...plus GFV = £27,584.82
£6k down....48 months.....10k miles....£329.83 month.....GFV £12,532.50...paid over 4 yrs....£15,831.84....plus GFV = £28,364.34
£6k dpwn....48 months......5k miles.....£299.65 month.....GFV £14,126.40...paid over 4 yrs....£14,383.20...plus GFV = £28,509.60
So buying it outright makes no real difference at all as there is only £75 in it between the two figures over 36months although a bit more over 48months
What would bother me only putting down 5k of miles a year to keep the payments lower is come trade in time the car doesn't actually make the GFV as you have excess miles on it, as VW gave you a figure for 15k miles whereas you have done 30k miles.
Although in saying that, with my last 2 PCP deals, every salesman has always looked at my GFV and just given me slightly over it.