Hi, if you're not intending to propagate from them, leave them whole, and if necessary get larger containers, Derek.

Thanks for the dahlia advice

Moatrat

Never sure. How to say thankyou

Hi Moatrat, this is the right way, just have you've done here, Derek.

Get them out of the container, wash off all the soil, cut away the fine roots and dry them off. May not need to get a bigger container when the the soil has gone.
Once dry, store them in dry peat or compost over winter until March when they can be started off .