Or try this...
If you have well-drained soil and live in a mild part of the country, dahlia plants can overwinter successfully in the ground with just the protection of a thick mulch. However, slugs and snails can remove new shoots in spring and there’s a risk of plants rotting in a cold, wet winter. The alternative is to wait until plants have been knocked back by frost then dig up the tubers, label them and store in barely damp sand or old potting compost in a frost-free shed or garage over winter ready to pot up again next spring.