I did not assert that Britain was completely isolated from the continent, but rather that there was a degree of isolation which is represented by EB as attested differences between the Casse faction and the british roster compared with other continental Celts. Myrcharn, and the Chariots, are part of it, and the description for Myrcharn does not attest Belgae origins.

Saying that the British military was "less" developed is certainly a subjective matter, of course. The fact that they used technology classed as outdated for armor and preserved weaponry and styles that were lost on the continent can certainly be argued as such, but I am not as versed in Casse, or in Keltoi history, to confidently affirm this on a wider view. Myrcharn were, as their description attests, a rare and secondary auxiliary component for armies dominated by infantry. That fact however does not preclude they would remain outdated, but rather merely as a minority. If the fighting styles and training of British native cavalry could not compete with continental cavalry under the service of Briton warlords, they would quickly become irrelevant and adapt the continental styles at least in the better developed parts of the isles. So the existance of both Myrcharn and Curepos as mercenaries may be self contradictory at first light.

I would be happily proven otherwise by the Casse team, though.