I've just fitted some 205/55 R16 Mondeo wheels about 1 hour ago along with new brake discs, pads and a nearside front ABS sensor. I used the above mentioned website to get my information as well as others. I found this one to be a good and was the most help in trying other sizes as it gives a recommend a MAXIMUM of +/- 2.5% difference Changing Tyres Sizes - Tyre Size Change Calculator
I also tried a good friends Mondeo 225/45 R17 but was unable to fit as they caught on the inside of the rear wheel arch, The offset on them was ET38. I didn't try the front to see if they caught on the steering. I then thought of going 215 but was told that there is approx 7mm difference in tyre width to the 225 so I took the easy option and fitted 205/55 R16 6 spoke Mondeo alloy wheels, They look great on, I think they look better than they did on the Mondeo.
I did have to make one modification and that was the Alloy wheel centre hub cap did not fit on the rear wheel to start with, as (mine has disk brakes on the rear) the rear hub bearing cap fowled on the plastic hub cap. This was soon remedied in 5 minutes with a copper hammer and knocked the areas that where fowling. Also don't forget you need 91 or 94 weight tyres for the Connect.
I paid £125 for mine inc. 2 tyres with 7mm and 2 tyres with 4mm out of our local Adtrader
I also found out that S-Type Jaguar wheels will fit and the later Volvo V40 V50 & V70 wheels fit but 1st check they are 5 stud 108 and the offset is correct as one set of Jaguar wheels I looked at had an offset of 60