The British Iron Age is often considered to have ended (and defining historical periods is iffy at the best of times ) at the time of the Roman Invasion in the early 1st Century AD. This is at least in terms of technology, architecture and social patterns.

The Anglo Saxons began to arrive arround 450 AD, filling the vacuum left after the Romans evacuated their troops from the Island due to internal and external conflict. It was a gradual process but after a couple centuries the Anglo Saxons had attained much of what we commonly consider England, though they were divided into separate kingdoms and would not be united under one ruler until the 9th and 10th centuries.

However it should be noted that some Iron Age practices, beliefs and customs seem to have survived outside of the major population zones, partially due to their isolation and insulation from other practices. So your slides drawing connections between the British Iron Age and the Anglo Saxons may be in reference to this. The people who would have been continuing these customs would have been out of the reach of the Anglo Saxons (or the Romans for that matter).

Hope that was helpful.

I'm sure you already have some material on burial traditions during the Iron Age, but I can recommend some further reading. The books that I would consider most helpful would be:

Higham, Nicholas J., and Martin J. Ryan. The Anglo-Saxon World. Yale University Press, 2013. This book is a good interdisciplinary overview of the Anglo Saxon time period in England, which examines archaeology, technological development and traditions in addition to the more widely known historical approaches.

And

Jones, E Michael. The End of Roman Britain Cornell University Press, 1996. This book delves more deeply into the burial traditions and archaeology of the time period, which obviously you seem to be interested in. It might help clear up how some British burial traditions continued or changed during the Anglo Saxon time period.