I bought a Connects2 iPod for my current gf's Focus, and my ex's Puma - both same Ford units so I knew how to fit the second one easily lol) and got both of those from eBay used. One tip is make sure, if you're going to do it in the dark. the cable isn't dangling out of the door when you close it - I had to bodge my gf's one back together after crushing the end - occasionally one side of the speakers doesn't work at a time, usually fine though lol.
Always had positive experience with Connects2 adapters, though it's not always great on the radio display (it doesn't know what track number it is so will go up to "01-03" when skipping but always goes back to displaying "01-01" lol. I use the iPod itself to control it anyway so it's fine.
It's a shame the 156 doesn't suit aftermarket headunits as I had the Alpine x001, X305S then the double DIN version W404R in the past and they're made purely for iPods and they were fantastic!