Gillian,
Will you be doing your piece by hand? So many people have embroidery sewing machines now!
Sorry, I don't know of a site, but you could try a Google search. I'll try to pass on what I know ( I used to teach an embroidery class)
An outline (stem) stitch with 3 strands of floss works best, but you could use all 6 strands if you wanted a bolder look.
Small areas can be filled with a satin stitch. This is done by making side by side stitches, just up and down till the area is covered. (If you strip the floss- meaning separating the strands, then smooothing them all together again- you'll end up with a very smooth finish. Looks like satin

)
Larger areas could be filled with a variation of a satin stitch, called a fill stitch. The satin stitch is worked in varying lengths across an area to be filled in, in a row. Then you do another row beneath that matching the stitches from the previous row.
Depending on the design, large areas could be filled with little flowers and french knots ( like a dress--you would outline the dress, then fill in with tiny flowers, making it look like a print).
I don't know if this helps, if I come across anything, I will try to post a link.
Loretta