I have come across a 3kW portable convector heater which
could date back to that era, which is rather ironic as
you'd be hard pressed to find one over 2kW nowadays.

Both mine and my mother's fan heaters are 3kW. They're pretty widely
available. However, the cheapest in the range will be a 2kW, so they're
probably more common to find, as most people are cheapskates.

As for convectors, a quick browse of argos shows five 3kW, one 2.5kW and
four 2kW models available.

Christian.