I have a Hallam (348 last) and a Weymouth (337 last). Apparently these are some of the more generous Lasts - especially the 337. There is a thread out there where someone posted an order of what was narrowest to widest. I just can't seem to find it right now but it was helpful for me when I was looking at the C and J line of shoes. The Hallams (10E) are a bit on the narrow side for me and I am a 11 D fit in US size pretty consistently. My point is that not all of the C and J are narrow but my suspicion is many of them are.

 

Hm, now that you mention it I think I've seen that narrowest to widest comparison aswell. I couldn't find it again when I started looking though.
OK, sounds like it might be risky for me to order a pair that only comes in the E width then.
It seems the 348 are bit longer and more narrow than the 341. So the 341 may fit me well. The thing is, at first I thought size 7.5 would be the one to go for but if C & J generally are a bit narrower than say, Church's, maybe I should go for size 8. And hope for them not being clown shoe long, hehe.

 

I found the thread where a bunch of C & J lasts are ranked from narrow to wide.

This is the "final" post in the matter in said thread: https://www.styleforum.net/t/135437/crockett-jones-238-last#post_2414896User mg428 ranks them like so: (most narrow) 238 < 324 < 317 < 348 < 240 < 330 < 337 < 341 < 236 < 318 < 360 < 325 (widest) and it's pretty consistent with what I've been reading in other threads where the last sizes/widths are discussed.
Note though that the ranking is concerning width only, 348 is a longer last than the 337 for example.

Also worth mentioning is (and I quote mg428): "... unlike the lasts narrower than 337, there are small incrementals amongs that lasts wider than 337, meaning that I would not say one is substantially wider than the other.".

 

My data suggests the 360 by Crockett & Jones in 7.0-E won't fit well, given the shoes you wear. You may need to try the 7.5-E.

I have no data about the 341 last, given your shoes.

Hope this helps.

 

The Crockett and Jones 341 is a narrow last, very tapered, but it is also a longer last, which means the tapering happens further away from the heel--which makes the toes feel a little less constrained. I think if you fit the Park Avenue last from Allen Edmonds in D width, you will probably feel comfortable in 341. You might consider ordering half a size up if the Park Avenue is on the tight side.

With Crockett and Jones, however, I would highly recommend a trip to the one store in the US (in New York). They fit odd, until you find the one that fits. Moreover, your order from England may take weeks or months to fill because of C&J's demand and strange ordering policies, and it will cost you to return them if they don't fit, and then you have to reorder, wait, etc. I would wait until you are in New York next and try them on. The salesmen there give generously of their time and will help you try on every variation they have until you find what you need, and they will also order shoes for you and send them along.

Alternatively, the chukka boot from Peal and Co (Brooks Brothers) is a C&J make on the 341. You could order that one online from the states and size it up.