Personally I don't believe you can use an actual R32 exhaust but I may be wrong, almost all the big VAG exhaust makers do an R32 exhaust for the GTI brand new they can be up to £500 for a cat back, milltek and BCS do the top quality ones, but you can often pick them up second hand for less than half depending on condition and milage, if you only want the look then just the cat Back will do
For The bumper you will need to buy a genuine R32 bumper, it will fit straight on to the existing mounting points that the GTI bumper is on, don't go for a cheaper eBay option as they are poor quality and don't come with a heat shield to protect the bumper, you can pick these up for about £150-300 depending on condition of the paint, obviously getting the right colour can make It tricky but it's not too expensive to get one re sprayed the right colour especially if you do the prep work
Hope this helps!