I picked up a job lot of old (really old) AVOs a couple of years ago. One of them had UK mil markings (the prisoner's arrow, or W ^ D). I gave it to daughter 1's FIL who had always wanted an AVO. I couldn't see which model it was.
If I really care about waveform (sometimes I do, mostly I don't) then I fetch the oscilloscope from under the desk. Most of the time, the RMS fudge factor will do me nicely.
I was told last week that the UK mains supply now has to be a minimum of 220V (not 230, nor 240) at the meter. We just had the overhead cables to the church moved underground, and the contractors were grumbling about the heavier-duty cable they had to use because of the length of the run and the load we put on it. I think that explains why the lights used to dim when we turned the heating on.