I've sold a 2007 Polo last year with 8K on the clock.
A couple came from wales to look and buy it, she asked if she could pay £1500 cash and then the remainder by bank transfer, so we went inside and went on the laptop and made the transfer, money was there in 45 minutes and she drove off.
For your GTI i'd insist on Cash or bank transfer, as the buyer can come, place a deposit, then go away and make the internet transfer, and come back when cleared?