On another mailing list I'm on, one of the members posted a notice about the following book. It looks pretty interesting. Not too terribly expensive. I'm going to see if I can get the book through interlibrary loan. I am very interested in seeing the discussions on temple design.

From the Oxbow Web site (UK version):

Religious Acculturation and Assimilation in Belgic Gaul and Aquitania from the Roman Conquest until the end of the Second Century CE
by Alasdair Watson

This volume sets out to prove that, far from being simply assimilated or subsumed into Roman religion, Gallic rites continued, and continued to be the basis of Gallo-Roman religion. The number of these Gallic beliefs and customs which continued after the Roman Conquest is examined and it is demonstrated that, for example, Celtic sanctuary design was the basis for Gallo-Roman temple design and that Gallo-Roman religion continued to be Gallic as well as Roman. 260p b/w illus (BAR 1624 2007) 9781407300368 Pb £38.00