A few good dealers around I think and it seems like Bauer Millet from Manchester is very good (from what I understand)
In London I would NEVER use the Marylebone one as their customer service is incredibly bad. I used the guys in Croydon and found them very helpful for my LE. They have very few customers who will go to them to buy a 4C I believe based on their location (pretty grim) and that is a major plus point IMO as you will be a "special" customer for them.
If you need specific contact names for the Croydon dealer or Bauer Millet PM me.