Dave Liquorice has brought this to us :
The phase feeding that small terrance has a problem. One of the other
phases feeding the other block is OK. With 173 incoming I'd switch
off at the main breaker and call the REC and report it. Some kit may
object by letting out the magic smoke with such a supply. Other kit
will start just draw more current and your cooker/fan heater
experiment indicates that there is plenty of current available, just
that the voltage is low.

I would not expect an entire terrace to be on one single phase. The
other block might well be on a completely different supply. Whilst they
do feed single phase premises one phase then the next phase, then the
last one - there is no absolute rule to be relied upon. They might well
have fed two adjacent premises of one phase, then the next two of the
next phase and so on.

Low voltage (a brown out) could simply mean they have had to load shed
in a certain area due to a cable fault, or it could be the supply cable
itself has developed a fault. Another possibility (especially if the
voltage is varying) is that there is a break in the neutral So the load
is simply balancing itself across the phases - which means if you have
lower than spec voltage, someone else has higher than spec voltage.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk