I own a pair of Swanseas on the 341 last in a U.K. 10E. The shoe is too big, I own a pair of brooks cap toes by CJ on the 341 last in US 10.5D.
How should I size marlow?
Correct, it will be in UK sizing. I can't say how it compares to the 341, but I checked with Lauren about comparing it to the 335 last and this is what she replied:
"In regards to the fitting of the 325 and the 335 the 335 fits ever so slightly bigger in comparison however this is not a great deal so we would not recommend that customers would change their sizing's when going between the two different lasts. The 335 tends to be a little longer in the toe box, however this would not affect the fitting enough to change the size."
Hopefully this information is helpful to some.
I actually like that idea. They will do the wheeling on a double leather sole but with flat welting?