Re: 147 vs 156, personally, I test drove several of both, varying engine sizes etc. My bro. also has a 147 1.6, and we both drive on Irish roads.
I loved the 147, and it was a really tough decision in the end, but I went with a 156 1.6 - better drive (my opinion only) and just that little bit bigger - plus, as most of my time is spent in traffic, the 1.6 made a lot more sense than anything bigger.
Thing is, you dont want to get the basic model, even though its only 1000 or so more than the 147 - the 1.6 Sportivo adds a couple of k to the price, but it's well worth it - 16" alloys, aircon (I got a sunroof instead, but that was my choice), carbon console, skirts etc., plus a slightly different suspension setup - not "soft" like the regular 156, but just somewhere nice in between - feels like its well planted if you know what i mean...
If you do decide to change, best of luck - keep in mind that if you do get the basic,basic 156, you'll probably regret it after a couple of months when you say to yourself "I wish I paid the extra couple of k..."