Intermittent miss fire

[<NickArg@domain.elided>]

Well the summers finally here in Cambridge (30+ degrees C) and
my Stag has developed a miss fire

Here's the symptoms:

Temperature gauge in centre, it goes above centre when
idling in traffic. Ticks over fine. Pulling away get over 3,000 rpm and
the engine starts to miss. After changing  up  it stops missing until
3,000 ish revs then the same. Once  the temp gauge drops to 
normal no more miss fire what ever the rev's

Every time I have to stop for traffic lights etc. the same thing 
happens. 

I ran the car this evening and everything was OK. So any
suggestions where to start? I suspect some form of fuel starvation
when hot.

PS The car cut out completely one day last June after I left
it idling while checking the tyres.  The fuel pump was 
clicking madly, but after a minute or two it stopped clicking
and the car restarted .

Any connection? 

Regards


Nick