BERLIN, Oct 5 - German firms with a presence in Britain or Northern Ireland must make provisions for the possibility of a "very hard Brexit", the BDI industry association said on Thursday, adding it was concerned at progress in Britain's divorce talks with the EU."The British government is lacking a clear concept despite talking a lot," BDI Managing Director Joachim Lang said."German companies with a presence in Britain and Northern Ireland must now make provisions for the serious case of a very hard exit. Anything else would be naive," he said.