I have the standard Q2 18" alloys on my GT for the summer and a set of 17" Q2 17" (147) alloys for the winter - with winter tyres obviously. Handling-wise, the higher offset is fine (chassis is essentially the same a a 156 wagon anyway) and it helps keep the winter salt spray inside the arches. However, you can tell visually that they are a bit further in than they should be.
Interestingly, although they seem very similar in appearance in a photo, when you put them together, the details of the design of wheels are quite different. The "spokes" on the 17" wheels are much more curved.
"When you sit in a Focus RS or a Golf R32 itís like sitting in a commercial for Lynx aftershave. When you sit in an 147 GTA itís like sitting in a Venetianís hand-made suitcase." J.Clarkson 2003.
Current fleet: 156 Sportwagon jtd 16V (facelift) 2.4 Spider, Leon Cupra SC
Projects: Spider S4, Matra Murena 2.2