Maybe gravitas isn't what I'm looking for.  Maybe supercilious without the arrogance?  That thing some Brits can do where they can likeably get away with saying, "Yes, because I'm  British."
I kinda want somebody like Matt Bomer without actually being Thoma- I mean Matt Bomer.  In the sense that Steed's defining trait to me (more than even his britishness) is that he can be obsessed with 
fashion while still being a badass. 
Dapper.  Thats the word Im looking for:  Chandler Steed needs to exude "
Dapper" from every pore
A Neil Patrick Harris, or maybe a well-groomed Orlando Jones?  or OOOh!  Taye Diggs!  Can Taye Diggs do a British accent?  Id also be fine with Chadwick Boseman playing it light and British like he did in Gods of Egypt.