Mate, at £23 a CFL you might want to consider saving for a HPS/MH. Do you have the space? Only £65 or so for a cheap 250W ballast :)
My setup is a cheap as they come for a 400w self watered (groan) system. Say £90 for a cheap ballast and hood, 2 bulbs at £10 each, Nutes £25 grow and bloom, £10...