I might answer a question with a question.
Do you consider the C you wear to be a medium size or a narrow size?
I suppose I describe my US width as medium = D.
In the UK either E or F can be medium depending on the shoe. Some claim that the EG D (in the 202 or 606 last) is medium. I suppose I disagree with the latter in my experience (only one UK sourced EG that is a E width that fits me nicely.)
After buying a bit over 20 pair of shoes this year from US, UK and Italian manufacturers I have come to believe that what we call width has little to do with the fit of the shoe. What is important is the volume under the vamp at the widest part of the shoe.
US shoes tend to have low volume since they are built for a relatively low toe box/vamp area. UK shoes have slightly more volume in that part of the foot and feel wider. Italian shoes are even more in that area. In fact unless you have a particularly high instep you may have to size down significantly on an Italian sourced shoe.
The best bet is to deal with someone at retail with an excellent return policy or to go to extraordinary lengths to try on the shoes before purchase.
I bought some C&J and some EG by mail order and luckily they fit, but a fair bit differently than I expected. And I already owned US sourced C&Js and US sourced EGs (both Polo branded). Yet I found the UK shoes roomier.