To ask how the heck I start a build project?

[allotmentgardener]

At very early stages, want a loft extension and extension of the kitchen diner with new glass garden doors etc, and have had 2 architects round. Got a quote from one with no initial sketches that seems pretty steep, and the other says he will do a few rough sketches having downloaded the plans from the web then pop round see what we think before doing a quote. Is it normal to instruct an architect with no initial sketches?
Then what happens next? Planning yes then instruct a builder but where are the pitfalls and problematic points? I dont have a clue where to start! Please help MN gurus!

Do the architect quotes include structural engineering, surveys, planning permission, redrawing if required? do you have a project manager or are you planning on managing it yourself in which case you should do a lot of research (there are courses & books). Is there anyone local who's had something similar done, in which case can ask for recommendations.