Not a bad price at all...
Did you get the fitting kit or just the skirts..?
If you already have the GTI with side skirts then you will already have all the fixing kit on your car.
Just looked up my invoice.
Sideskirts were £38.03 excluding VAT so make that £45.63 each
Fixing adaptors were £4.40 excl VAT so £5.25 each (you need 4 off)
Fixing Screws were £0.33 each ex VAT = £0.40 each (you need at least 4 of these also)