Commercial transformers are built to a price,(e.g. economise on iron and copper). A small increase in supply voltage will push the core into saturation and the losses increase dramatically. A combination of several effects lead to poor secondary voltage regulation. In power distribution it is inevitable that consumers close to the distribution transformer can get a much higher voltage so that consumers at the end of the line get the nominal voltage.
Overcome all transformer related problems by using a voltage divider connected directly between the active and Earth. The current drawn by the voltage divider is small enough that Residual Current Devices are not affected. In an M.E.N. power system the voltage between the neutral and earth is negligible.
If you really require a transformer then get a proper voltage transformer.

TG