If the need is desperate, you will have to do it, but usually, when a plant has outgrown its pot, you need to rake out the roots from the coil they will inevitably be in before you put in a larger pot - if you do this now, you will probably lose the flowers. If you decide to do it anyway, it will flower a bit later instead, when its recovered.

as long as you water it well and for several days/weeks it will recover. Bamboo is correct you will have to tease the congested roots out and this damages the fine root hairs that they use to take up water. But if it really cant wait till after flowering you will have to 'bite the bullet'.

Thanks bamboo and seaburngirl. I will leave repotting for now as I would rather have a fabulous flower display this year.