Hi, I think that Somerset shared quite a lot of what was happening in the southern part of Wales, the only thing is we just lost a lot of our stuff along the way. High ground was the only place to settle in some parts, prehistoric trackways reflect this. The west entrance of the Littledown fort focuses (the original prehistoric track) on a pass between two ranges of hill that point to the south coast of Wales, in fact you can see the Bristol channel and the sea on a clear day.
FWs post, that circles did,nt dominate is probably right, but you have only to look at Grays Hill above probably another pass, looking down at the later Caerwent and the famous Caerlon to find the interconnecting pattern of settlement..... and
if you look at the following photo by Eternal, its pretty obvious that we all travel the same way..
http://www.themodernantiquarian.com/post/42951
track through pass, its boundary/territory?/ settlement area , and modern road.. highlighted by barrows.