Simon is using a MSSQL (SQL Server) database. SQL Server does not have a sql dump function like MySQL does. Unfortunately, you can't easily dump a SQL Server database to a text file, do a search and replace and then import the fixed dump file back into the database.
There are a few SQL Server "search and replace" scripts out there on the internet, but the ones I've tried have all generated less than pleasant results. I certainly wouldn't use them on my production server...
In addition, Simon is running Moodle 2.4.5+, so he probably still has all those dreadful NTEXT columns in his database. Those NTEXT columns can't easily be searched which makes a "search and replace" script trickier (this is fixed in Moodle 2.6 where those NTEXT columns are converted to NVARCHAR(MAX) columns).
So we really do need something like the "Search & Replace" tool in MDL-35099 (so please vote for it!)