As tox said none fit without modification! You can get the rear "bottom" parts to fit only just, but one hook doesnt line up properly and they are very tight agains the rear speakers! The rear "back" parts dont fit at all! You can get the 3/4 in slighly( about halfway) but the 1/4 part in no chance, for it all to fit correctly the whole rear bench would need cut down! Also they wont lock in place, and I dont know if they need to for mot etc, I recon it isnt very safe and really isnt worth the hassel!
As for the fronts, recaro do make a subframe for the polo 9n but only for non standard recaro seats, ie one's you can buy from a shop etc, the recaro subframes wont fit standard equipment recaro seats, ie one's fitted to golf gti's etc as standard! To make them fit you will need to strip the whole subframes then make up brackets then weld them to the base of the new seat, then bolt them to the floorpan! Also some seats come with the seatbelt lock welded to the seat, this would need to be removed then re attatched to your new seat!
Everything is possible if you have the time and know what you are doing!
it can be done