First step, check out the sticky at the top of this section,http://www.tomshardware.co.uk/forum/277130-11-read-first-watercooling-sticky
Decide what you are cooling, Cpu only or Gpu as well?
and whats the maximum budget here?
You may be able to build a custom loop for similar money,
Kitwise though check out Xspc.co.uk, they have some excellent kits to get you started in W/c, avoid thermaltake kits, they have aluminium in them and likewise any cheap chinese kits,
but read the sticky and see what you can come up with yourself, we'll help you with choices and steer you right but we can't build it for you