If you're feeling a little adventurous you could try an EK or XSPC kit. They retail for around £130 in the UK. In the EK one you get everything you need including coolant. In the XSPC kits you get all the parts and only need to buy some coolant yourself (which is about £5 for 1 Litre of a good premix)
If you don't want to go that way then as you pointed out in your post the H100 is a good sealed unit. There is also the asestek model linked above by JMMP which is basically identical to the H100 but you may find that in shops a little cheaper than the Corsair unit.