Central heating pipes - minimum clearance to other pipes

[billyzzz]

Hi,
i am currently having central heating installed the people who are installing it are Corgi certified. I had a question on the central heating pipe routing. What is the minimum clearance required for the central heating pipes from other mains water pipes and gas pipe (copper type) ? Does Corgi or any other body have a recommendation on the minimum clearance required?
Thanks,
Billyzzz