in the end I narrowed it down to just 25 reports that needed fixing (urgently) so I have done it the long way round. These fell into two categories. The first were just 'badly' coded and didn't need the 4 part name. The others were using the DW as the main data source but the query reached back into the OLTP database for some stuff that was not in the DW and was therefore a linked server and these still need the linked server but the server name has changed. I guess the 'proper' way to fix these would be to use synonyms and map the synonyms to the linked server tables (or put the stuff in the DW in the first place!)

at least by downloading them from the report server and editing in BIDS, I have copies of the before and after images. One problem we have is that at least three different developers have had a go at some of these reports and so there is no guarantee that the copy on your local machine matches that on the server. How do others do source code control for reports. Do you have one project that contains all the reports one project per report / report area, or do you just source code control the .rdl files?