Hi
These days the gauge is usually quoted in metres (1.414 is often used in Network Rail standards, but I have seen it as 1.44 and 1.4 which are probably just typing errors. ).
Anyway, the space between the running rails is invariably referred to as "the four foot". The space between two sets of these is, again invariably, called " the six foot". If there are two sets, eg Up and Down Slow and Up and Down Fast (can be in any arrangement) then the space between the pairs of pairs is called "the ten foot".
These spaces are never the exact distance and sometimes a very wide "ten foot" is referred to as "the wideway", although I think this is not an official term as the six and ten names are. The important thing to remember, in extremis when all the safety precautions have failed and you are stuck with a train aiming for you is "Lie down in the six or ten foot - never, never in the six!!"