dividing primroses

[tomatoada]

I am moving my drumstick primroses from the borders because they are growing over the annuals.  I have a spare bit of ground by the greenhouse. 
They have increased in size and need dividing.  Can anyone tell me when it is best to split them up, now or when I replant them in the borders?  Also when is the best time  to put them back, Autumn or Spring?  I have only had them 2 years and left them where they are last year.  Thanks for help and advice.

[tomatoada]

[Tee Gee]

Have a look in here;

http://www.thegardenersalmanac.co.uk/Data/Primula.htm

[Robert_Brenchley]

They like moisture so it would be better to wait until the heatwave is over. I'd do it in autumn or early winter.