Try the excellent Danish site dvdoo.dk, I have ordered from them several times, the prices shown are inclusive and delivery usually takes just 3 days. They have Gattaca for sale at 119 kroner which works out at approx £9.60, I doubt you will find it much cheaper anywhere else and of course it`s R2.
http://192.38.242.50/dvdoo/film.asp?Command=2367