Yes they can - but finding them (new) is next to impossible. I couldn't find a part No for them anywhere and neither could Autocool.
I struck lucky that one of the Autocool techs had one in his 'bit box'. Later ones have a different thread size. I think most people replace the pipes complete.
But before you do anything else I would find out which valves he as talking about, I've never been any sort of a fan of Kwik**** - go to ATS and tell them what's happened - competitive spirit should kick in
Good luck.
Never been a fan of Halfords for mechanical work (shops ok) but got into my elderly Focus the other day after finishing work, was a very hot one, and just swung in on the spur of the moment as it is on my way home, regassed it while I waited there and then, £49 guaranteed for a year, was impressed, works a treat