The heater blower on my 52 plate Civic has stopped. I think it's the resistor pack or the owed motor itself. Curiously it restarted a couple of times.
Do resistors fail totally or intermitently?
How could I test if the motor if on the way out?
Any advice welcome.

When the resistor pack goes it usually only knocks out one or two speeds it will still work on full blast.

The switches can fail or more likely the brushes in the motor are stuck and don't make contact with the commutator.
Usually if it is the brushes giving the motor a light thump shakes loose enough to get the motor turning for a while.