Do you plan to use CSS for setting the headers?
In this case, I would suggest a careful treatment of Trebuchet.

Yes, CSS to set the headers, so you suggest calibri as the headers and trebuchet as the body?

Thanks

Simon

No, I personally don't like much Trebuchet for body text (too "fat"). For text I think you could use the "classic" Helvetica/Arial stack, or even a serif one.
I meant Trebuchet for headers.

Ok thanks, I'll try that then, if i embedded some non web fonts, would you suggest any different?

Well, of course it depends on the content and style of the website, if there are other places (stationery, etc.) where the logo will be paired with other typefaces, and so on.
First thing you should determine is if you want Calibri just for the logo or as "corporate face" (pull-out, etc.).
You could also try to define it in CSS, but the problem is that it's pretty small compared to most other fallback fonts.

Yes Calibri for as you say (corporate font). In terms of style of the site, Im trying to create a clean professional feel (colours black, white, magenta) black/dark grey background with white/off white content area. Headers/Focal Points in Magenta, so will stand out quite a lot anyway, so I dont want a type that is too heavy really or the over use of magenta could become too much.

Do you think I could use a slab serif type for headers and it look right with Calibri as the logo type font?

Thanks

If you want to use a slab, you will need images/SIFR or more modern solutions.
Then, I would suggest a slab from Luc(as) De Groot.