Mick, good pres are expensive usually, but you shouldn't need an expensive one for a decent sound. The focusrite you mentioned has great reviews, and is "affordable". I bought a Joe Meek meequalizer and despite the brouhaha about Joe Meeks it wasn't worth a flip, and I haven't used it in awhile. I think I might have broken it (accidentally/on purpose). I blame my brother; he recommended it. Their higher end models get pricey. Check this out: http://www.line6.com/toneport/vocals.html
I don't like Line6 guitar boxes, but maybe this vocal contraption will help.
The problem is this. If you can't sing, nothing will help. I get the most mileage out of getting the right mic, and that certainly doesn't have to be expensive. Next, use a great pop screen. I have a double pop screen thingie (forget the name of it now), and it's literally bullet proof for plosives. No more popping the pees. The mic that has worked for me consistently is a Rode NT3 condenser, and it's not expensive. I don't use a pre for it, just straight into the board. It is very sensitive, maybe too sensitive but if you tweek the inputs to match your voice volume, it's a beauty.
I'm sure David will know a lot more about such things.
