The liquid PC

If you ever need clarification on anything aqueous, better ask a fish fancier. Like Stuart Capewell for instance:

It may be a sad and nerdy piece of information, but the article in question mentions using an Eheim pump to force the water through the cooling block, but says the guys trying this can't locate the correct tubing to allow them to connect everything together.

Instead of trying B&Q, they should try their local aquarium supplies store - Eheim are one of the largest manufacturers of water circulation & filtration pumps for use in fishtanks...

That's solved the problem then. Are you a tropical or cold water man?