I found the following info:

The quickest and most reliable way of propagating Sarcococca is with semi-ripe cuttings in late summer/early autumn. You can also propagate by sowing seed but if you have a number of cultivars there is likely to be some variation in the offspring. You will need to clean the seed from the fruit first and then sow the seed no deeper than the size of the seed. Place in a shaded cold frame and expect the seeds to germinate in spring.

I've had success by taking the flesh off the seed so give it ago.

Ta!