We have control of all of that through the admin interface here:
The issue is not so much changing the logo, it's what to change it TO.
Chloe has been working on a variant of the logo she created for us for some business cards:
The colours are reversed to match the style here (i.e. black on white) and it's trimmed down, but she's not happy with it yet. She's also been super busy with work, and on top of that has been battling this awful cold for the last couple of weeks, poor thing.
I can supply the source files for the above if you wanted to have a poke around.