Are you sure you've got your sums right?
Converting everything to kilos, as I find it easier to understand...
Your PR1.2s come in at 20.63kgs which is heavier than my Turinis @ 20.4kgs. I thought the PR1.2 is a lighter wheel? Granted, you may have heavier tyres, but I'd have expected sub-20kgs.
Volks are 6.67kgs for an 18x8. Knocking 9kgs (source Rimstock's
website) off your PR1.2s combined weight means that with the same tyre your Volks will come in at 18.30kgs.
Rotating mass gives roughly a x4 effect, so that will give a total saving of 37.28kgs over your PR1.2s or 82.18lbs.
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To put that into context, at least £70 per kilo saved.. Seriously, I'm all for weight saving, but that just doesn't make sense to me unless you're completely stripping the car out and therefore achieving a higher percentage of overall weight saved.
That said, Neuspeed make some very lush forged wheels
http://www.vwspeed.co.uk/volkswagen/parts/Mk5_Golf-623-1.html