Gilbert de la Tour of Dorset bore "Azure, a tower argent, embattled and domed, the port gules". The de la Tours married into the Russell family of Kingston Russell in the early 1300s (Eleanor de la Tour married Theobald Russell as his second wife and they had a son, William). Not certain how the arms might be transferred in such a case, though. I can't trace anything else on the de la Tours, but it might be worth following that lead if you can.
These arms would be blue with a silver tower, not red.
"Patres nostri et nos hanc insulam in brevi edomuimus in brevi nostris subdidimus legibus, nostris obsequiis mancipavimus" - Walter Espec 1138