@PeterJarvis You can cut down the stems that have flowered to the ground. You are in a warmer part of the country so I would leave it now until spring. It it is wet over winter you my get some blackened leaves. In the spring you will see new shoots at the base then remove the old leaves. Years ago the advice was to tie the foliage together to protect it but they are fine through the winter in my garden in Notts. The aspect is south facing with fairly good drainage.
I have worked as a Gardener for 24 years. My latest garden is a new build garden on heavy clay.
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