I suggest one to visit the premises during weekday... And ensure you are going to buy something from them.They are real whole seller and doesn't like individual customer buying cut lengths in the first place.
The for the clarification.I mean asking swatches from the trimmings merchant e.g. RichardJamesWeldon or Dugdale.I believe Dugdale are slightly cheaper. I am not sure which are more willing to do with retail orders.
For cream suiting, go for traditional all wool worsted for the ultimate clean drape look.
I have used Dugdale Formal range before and I am very happy with it.
Linen and silk mix sounds pretty good as well.