Where did the angles and Saxons settle in AD 450?

There would have still been in mainland Europe in Germany during that era. However, they might, in that time period, have started to settle across most of England, probably excluding the very West of the country were the Celts would have been pushed back to.

The Romans stayed until AD 410, and when Roman rule collapsed, a century and a half of Immigration by Germanic peoples from European mainland followed ie. Angles and Saxons.