I haven't found anywhere that the had any clear contacts. Bede
(Anglo-Saxon) wrote on continental Saxons but he said precisely that
they had no relevant political organization: "the old Saxons have no
king, but they are governed by several
eorldermen (satrapas) who during war cast lots for leadership, but who
in time of peace are equal in power" (
Wikipedia).
It doesn't seem that British Angl-Saxons helped continental Saxons
during the war with the Franks (again no references). This could be
because more than two centuries had pased since they broke apart and
also because Anglo-Saxons were Christians, while the characteristic of
continental Saxons is that they fiercely kept their traditional
beliefs.