I used to have this problem.
There is a thread on here about it and how I got around it and If I get a chance later I'll try and find it.
In the meantime I can tell you that I went down a number or routes to try and cure it and in the end came to the conclusion that there is a valve in the fuel pump that has failed............not fixable other than replacing the pump
The way I got around it was to go into VAGCOM and change the car from a manual gearbox to an autobox. By doing so the ECU looks for a lower cranking speed and I've been running like that now for over a year. Always starts on the button now, hot or cold
The only issue I have is when using cruise control, the clutch is disabled so it doesn't disengage the cruise control when you press it.
