The Phase 1 report of the Rapid Coastal Zone Assessment of the Severn Estuary (well, the English side anyway) is now available from http://www.gloucestershire.gov.uk/index.cfm?articleid=16998
Phase 1 is the mapping, analysis and interpretation of all the visible archaeological features from aerial photographs. The report is a hefty download, but features a massive quantity of military archaeology, particularly second world war invasion defences. There is also a poster summarising a few of the more interesting military sites.