They're actually a miniature cathode-ray tube rather than neon, and work in much the same way as a TV or oscilloscope tube, on a more simplified basis.
Another common use was as a null or balance indicator. I have one used as such in an old resistance/capacitance bridge.
Operating voltages are pretty much the same as for the other valves they were used with, generally anything from about 150V upward on the anode (plate), although some will operate right down to 90V or so. The same goes for the other valves, generally 150 to 300V for mains types, but the valves designed for battery portables were made to run on a 90V HT battery. (I'm speaking of domestic radios here; TV sweep stages, high-power transmitting valves, etc. could run into the kilovolt range.)
Filament voltages in the 1950s/1960s era are most often 5, 6.3 and 12.6 volts, although others were used, mainly on power tetrodes/pentodes and C.R. tubes. (5V filaments were most common in rectifiers.)
In the British/European valve coding of that time, the first letter indicates the filament characteristics. The "E" in all the above examples means 6.3 volts. The American tube coding also uses the first number to give the filament voltage, e.g. 6SN7 is a 6.3V filament, 5V4 is a 5V type.
There are a few anomolies, e.g. the ECC83 actually has a center-tapped filament which can be wired parallel for 6.3V or series for 12.6V. It is a direct equivalent of the American 12AX7.
By the way, Tex mentioned the Brimar name. The name originated as a contraction of BRItish Made American Range, as the company was set up originally to manufacture American specification tubes here.
[This message has been edited by pauluk (edited 08-31-2002).]
