It never ceases to amaze me that people seem to think we have a vast number of medieval accounts detailing the history between any two groups of people and the feelings that these societies had towards each other over the centuries of their co-existence. On one hand it is intuitive that these societies which shared a common cultural origin in the aftermath of Roman collapse in western Europe would have some record of their mutual existence, I suppose. However reality is rarely so convenient.

The first thing to understand is that just because the Saxons, Angles, and Jutes were reputed by Bede to have called the lands occupied by the continental Saxons their home, and I will show that this was not even the case, it doesn't necessarily follow that they kept tabs on each other. The continental Saxons were largely non-literate and the Anglo-Saxons only wrote extensively following their conversion to Christianity over the course of the 7th century so sources are going to be difficult to find to begin with.

If we were going to base our understanding of Anglo-Saxon/continental Saxon relations on surviving textual evidence we would be in a spot of trouble, as the Anglo-Saxon historians, chroniclers, and so on barely seem interested at all in their cultural cousins across the North Sea. Our one, yes ONE, Anglo-Saxon history written before the conquest of the Saxons by Charlemagne makes mention of Northern Germany and the Low Countries only as a starting point for the Angles, Saxons, and Jutes in their movement across to England. Bede is not interested in recounting the opinions of the various Anglo-Saxon realms on the old continental Saxons, and its unlikely there was even much to tell. They probably traded with each other on occasion and that's about it. There was no shared conception of culture or religion or ethnicity binding these people together, and the conquest of the Saxons by Charlemagne goes completely unmentioned in later Anglo-Saxon histories.

The archaeological record is almost as silent. The Anglo-Saxon kingdoms in England developed new and more important trade and cultural relationships with other groups. East Anglia was connected to Sweden for example, and the kingdom of Kent was far more intertwined with the goings on in Francia than they were with the goings on in the Low Countries or Germany.

Because of the silence of the historical record, there is also silence from historians on this topic as well. It would be very difficult to write a book on the relationship between the Anglo-Saxons and the old Saxons in the near total absence of anything to actually use as evidence!

So with that issue out of the way, let me circle back to something else that I mentioned. We like to think that Angles, Saxons, and Jutes sailed to England, disembarked, slaughtered all the natives they could find and established their own kingdoms in the now empty land. These kingdoms then went on to coalesce into the Anglo-Saxon kingdoms of East Anglia, Wessex, and so on. This is the story that we are told by Bede, and is hinted at by Gildas, but it is a lie. Migration to England was not the purvey of whole tribes with their own distinct ethnic markers. it was a much less neat affair. Migrants from Germany and the Low Countries came to Britain in the 5th century yes, but the migrants also hailed from Scandinavia, Wales, Ireland, and Scotland too. Nor did they displace the native Romans/Britons. Anglo-Saxon culture was indeed something of a mix between the new Germanic peoples and the native British people. The kingdoms of England were not made of the same people nor did they share a culture with the people of Saxony in Germany. If you're curious about this transition from post-Roman Britannia to England, I can recommend a few books such as Robin Fleming's Britain after Rome or Peter Heather's Empire and Barbarians.

To return in a roundabout way to your original question however....the simple answer to this is yes, the Anglo-Saxon polities that formed over the course of the 5-7th centuries continued to trade, with no real interruption, with their distant cultural relatives in Old Saxony, Frisia, and Scandinavia. But as always there is much more to be said on this topic, so I will explain a little more about the differences between the Anglo-Saxons and the inhabitants of Old Saxony.

The first thing to understand is that just because the Saxons, Angles, and Jutes were reputed by Bede to have called the lands occupied by the continental Saxons their home it doesn't necessarily follow that they kept tabs on each other. Now while we know that trade did continue, as the existence of the "emporia" trade centers along the North Sea indicate, we don't have direct literary evidence of the interactions between the two areas. We know from archaeology that the trade goods likely included textiles (wool mostly), bone worked tools/jewelry, some agricultural goods, and maybe trading goods from other parts of the world as well. The archaeological record is almost silent in most other ways though, as only very small sites from this time period have been found and there is limited evidence available at them.