Q.Is it safe to plant out a potted Hebe in the garden in october
Plant about 18 inches high with lots of buds unfurling.
Accepted practice is to plant these in the garden in the spring. However, there are many varieties, so I don't know about the hardiness of yours. You might want to access the local Master Gardener organization. They have loads of information and assistance available for home gardeners. This link will help you locate the nearest group:
http://mastergardeners.org.uk/get-involved/find-your-nearest-master-gardener/
https://www.gardeningknowhow.com/ornamental/shrubs/hebe/hebe-shrubs.htm