Hi,
I have a similar problem with my 1965 2000, if the car is left for about 10-15 minutes it will not start on first turn of the key, (actually, the engine hardly turns at all before it fires up!) I usually have to crank the engine over about two or three times (a burst of 2-3 seconds each time on the starter motor - much less than most modern cars) before the car fires up. After about 1/2 hour the car will start without problem or within 10 minutes of stopping, absolutely fine. It does not matter what the weather is, winter or summer, always the same. My car is used every day, so well-used to the problem.
I read somewhere (Practical Classics Helpline?) that the modern fuels evaporate at the carburetor sufficiently to temporarily restrict the amount of usable fuel to & additional cranking is required on hot re-starts to pump fresh fuel through.
My car has a fairly new fuel pump and the ignition is spot on (Aldon Automotive electronic ignition) I am sure that this all helps get the petrol flowing again.
Worth checking that your fuel pump is in good order to maximise delivery of petrol and ignition is spot on.
If the problem is as a result of the volatility of modern fuels then you will just have to live with it, but if my experience is anything to go by, it should not be too much of an inconvenience - your situation is definitely not very satisfactory.
Good luck,
Gary