I noticed today that the pressure in my central heating system had dropped well down so I grabbed the blue plastic handle on the topping-up loop, and just as the handle turned through 90 degrees, the blessed handle snapped off in my hand!  Panic? I nearly died!  And the water is still rushing in, so I fled downstairs to where I knew there was a pair of pliers, and managed to grip enough of the remains to turn it off.
So, I need some advice please, gentlemen.  I need someone to tell me that I can buy a handle to replace the utterly destroyed one, and that I don't have to drain the system down and insert a new valve.  That way lies madness, or perhaps only bowel-wrenching terror.  All things plumbing are of the devil as far as I'm concerned - my Dad was a plumber and tried to teach me all his skills in a way that made me certain to never touch it again for the rest of my life.
Please show me the easy way out of this, or alternatively send me some Valium, 'cause that's the only way I'll be able to replace the valve. (bet it was a cheap Screwfix one!)
Regards, John the plumbing phobic.