Thanks to all.
To summarise what I have learned here:
Priming is fine, but do follow the perceived wisdom in the POH.
Pumping the throttle is bad (on an O-200); it doesn't help matters and following priming, may introduce too much fuel, in the wrong place, at the wrong time.
If the ambient temperature is very cold, prime according to the POH, but be very careful about doing any more if it doesn't start first time.
In cold weather therefore, if it doesn't go first time (or cuts out almost as soon as you release the key) what is the best option? Go for a 'flooded engine' scenario and get rid of the unburnt fuel, then wait a while and re-prime?
Any thoughts?