You'll probably get more help in the Lighting section, but you can get a good outfit for £1k. The brands to compare are Lencarta, Elinchrom and Bowens.
You need to be specific about what you're looking to do. Basic domestic portraits don't take much - you could get away with a couple of hundred quid. Or three quality heads, a nice big softbox or two, a background system and light meter - that will blow your budget in no time.