Hi I have a L.P.G bottle running a 3 burner portable stove, which is
designed to opperate on high pressure with no regulator. It has a
short flexible hose from bottle to stove. What I have done now is to
lengthen the supply line from bottle to stove by a few meters [about
4] in 1/2 copper tube and still use the standard flex for the
conection to the stove. This is where my problem starts, on initial 
light up its runs fine but if left a few hours say overnight it
appears to flood and controlling of the flame is impossible until the
line is completly
bled.

I will bet that if you go to 1/4 inch copper tubing your problem will go away.

hello tried that first with the 1/4 copper tube and the ruesult was the same.