I'm not familiar with UK cars but I presume this is an older car since
you said it has a carburator.  You have two pieces of data that
contradict each other.  If pouring a little gas down the carb allows
the engine to start and run for a few seconds, then there is
definitely spark.  If there is indeed no spark, then putting gas in
the carb will do nothing.  The best way to determine if it has fuel is
to detach the fuel line going into the carb.  There should be fuel
spilling out when you unloosen it.  A lot of fuel should flow out of
it if you crank the engine while the line is detached.  If there's no
fuel present, you know it's a fuel delivery problem e.g clogged fuel
filter, bad fuel pump etc.  Good luck.  Al