eggshell problem

[nailedit!]

Hi,
I want to paint a small area of wall with an eggshell finish paint (it's eggsactly (sorry!) the colour I want). It's going on over a silk finish emulsion.
I sanded & washed the wall, but the paint didn't seem to want to 'Stick@ to the wall, so I applied a coat of matt white emulsion, thinking that would help, but still no luck. Somebody suggested using undercoat, but I'd like advice before I try it please. Thank you.