Not firing when cold but will when warm?

Hi all. New to the forum but after reading through a lot of the threads I know I am in good hands when it comes to an awesome array of knowledge on hijets! Bertie came to us in march as a customised catering van (ex Phat Pasty for those who are familiar with them) and he was very poorly! After a lot of help, advice and long journey's for perfect parts (Thanks Woody!) We finally got him going and bursting into life. However.. he does not want to start first time when cold. He will turn over for a good 3 attempts before firing. Once running though he purrs like a kitten and when he is warm he will start first time. Many thanks in advance for your time on this thread.