Thanks for the responses.
From what I can tell the 2.1 sport edition came with 17's on. :-), I think originally 225/45 as they are slightly lower profile than the 205's.
I'd checked the fuel cap flap, but no sticker so I suspect that got snapped off at some point and replaced with an after market one.
As for the ride vs grip etc... What a spiders web. One review I came across commented on how better the 225/45 felt vs the 205/55 (which he'd driven on another model)
From my research either can be used and the wheel / tyre width isn't an issue. But as ever Getting too much choice... :-)
They do like to make it easy...