Nope, and I know a lot of UK stores. Unless you go with Aqua-Computer stuff, which is sold by
Wizard Designs, but that is a low-flow sytem and most likely not what you are looking for.
If you really worry about resricting flow, I would suggest not to watercool the NB at all. Advantages will be minimal; a Zalman passive heatsink will do the job sufficiently.