Hi buddy and welcome.
I'm going to tell you what i would do if i had £16-£17k(and its only my opinion)
Firstly i would'nt be looking at a gt model, yes you could buy a uk version but you would be looking at 53,04 and doubtfully a 54.
I would be searching for a non gt and looking at an 05 or 55, reason being is that they will still have the nissan warranty left on them,
as mentioned leather, bose etc etc(gt) are not everything they are cracked up to be.
I have an 04 non gt which i bought a short while back and still had warranty left, nissan replaced all 4 rays alloys and two brand new driveshafts, god knows how much this would have cost out of warranty .
Sure you will have a good time hunting, but the only thing i would advise is ...... take your time to find the right one.
Its also worth bearing in mind that whilst I would agree the GT extras aren't worth the premium (at least on a new Zed) others have found non-GT's hard to shift when they come to sell on. The market wants GT's.