Paying £60 for a tank of V-Power, I get average 400 miles to a tank, which works out at £0.15 per mile. £0.35 - £0.15 = £0.20 per mile, which is £6,240 if you're doing 600 miles a week for 52 weeks, or 31,200 miles a year. Now let's say you're going to need 1.5 sets of tyres per year, at £400 per set = £600, so you're down to £5,640 per year. Let's add another £500 in maintenance per year (and that is conservative), and you're left with £5,140. Times 3 years you're getting roughly £15,420 compensation for putting close to 100,000 miles on your pride and joy.
So it depends how much you paid for your GTI, how many miles it had on it, and how much you'd like to get for it when you sell it.
Having said all that, the popular wisdom (which I agree with) is that motorway miles are easy on a car, so the wear shouldn't be too much of an issue, apart from the increased maintenance costs associated with much higher mileage.
