I've heard that some GTi owners have had their alloys replaced under the
original manufacturer's 3-year warranty if they've had the car from new or nearly new. I myself had a 12-month warranty from the local VW dealership after buying used, but there was no scope for replacing the alloys or having them refurbed by the dealer because I only found out that it wasn't just my wheels when I found out about UK-P.net! I thought it must have been down to the previous owner kerbing them and not looking after them
Of course you can definitely make a fuss about them when you buy the car and use it to negotiate some money off, as a full professional refurbishment of a split-rim BBS alloy can be anything between £50-80 per alloy depending on what you want and where you go. Its much cheaper to just have the rim sorted out as this doesn't involve splitting the rim, so maybe £30-40 per alloy wheel.
As an example, I'm planning on having mine split, stripped down and refurbed in hi-power silver with a diamond cut rim, and this will be approximately £75 per alloy, which is £300 for all four - so thats quite a bargaining chip in a used car sale!