ill ask this for my sanity.
yes the cupra R bumper will fit.
however not without a little work.
for example the, wheel arch liners will need an addition bit so they they fit the inside of the bumper.
the foglights are different, so thats another load sof £s.. they are not cheap. however many people sell them second hand.
you will need new sentre top grill also i believe.
600euros sound alot for a cupra bumper, that about what an R bumper costs in the UK.
im sure you can get them for 380ish from the right dealer. (plus spraying)
as for height, the R bumper is lower but has a splitter at the bottom, (anoth £20 or so) this is removable and replacable.
you have 17" wheel the R had 8" but the radius is the same so the wheels make no difference to the height. however the FR suspension is not as low as the R so you will aactually be higher than an R.
do a search on here, there are many places the parts required for a swap to an R bumper are listed.
R bumpers second hand are hard to get hold of, but dont be tempted by the cheap copies, they dont fit and you will take a LONG time to get them to fit and it wont be right.