You can buy lengths of plastic in diy stores, cut it with a hacksaw and tidy up the ends with a stanley knife, hardly professional but it works (takes a bit of time though).
They look like 3/4 bsp tap tails, and these would do the job http://www.screwfix.com/p/flexible-tap-connector-15mm-x-3-4-x-500mm/96407 and the bore is large enough for a combi boiler.
They look like 3/4 bsp tap tails, and these would do the job http://www.screwfix.com/p/flexible-tap-connector-15mm-x-3-4-x-500mm/96407 and the bore is large enough for a combi boiler.