sounds more like the usual relay fault if you ask me, and possibly faulty ignition switch is another thing it could be
ignition switch would just be no sparky at all... would it not?
nope...
its exactly the symptoms of what mine did, intermittant working and genrally just pissing me off, if you messed with the wires on the back of the switch it would run, it also would run if you held the key on as far as you could
common fault on the 3 is the ignition switch, changed mine and its now fine (did this after changing all the bleedin relays)