Found a way to do this 10 minutes later and I thought I'd share it in case it helps someone.
There might be a "proper" way to do this within the program, but this way has just worked for me. The Prelude project file is just an XML document so easy to edit and this method should be bulletproof ( make a copy of the project file first though )
- Close Prelude
- Open the Prelude project file in a text editor, eg notepad but you'll need Sublime Text unless you want it to take ages or if it's a very small project
- Replace all the FilePaths with the new file path ( if you use sublime then it's easy to use ctrl-D to multi-select them all in one go but if you're not a Sublime user you'll need to do them one by one - only change the file paths fo each clip not anything else at all
- Save the file and open in prelude
Eg, for each clip you'll have something like
<MasterClip AssetName="back-head" AssetType="AssetTypeMasterClip" ClassID="9091c12c-9d39-43b7-b55e-4de81592552c" CreatedDate="11/27/15, 12:54:25" DropFrame="false" Duration="2542700160000" FilePath="C:\old\path\tozfootage\DSCF4661.MOV" FrameRate="8475667200" ImportDate="2015-12-18 03:04:59" ParentClassID="18e728c6-1583-44f4-96da-2a830cded31a" StartTime="0"/>
change the part where it says FilePath="C:\old\path\tozfootage\DSCF4661.MOV" to your new\path\to\footage
so you'll end up with FilePath="C:\new\path\tozfootage\DSCF4661.MOV" - and so on for the other clips
- in my windows 7 machine I can find the path easily by right clicking the address bar in explorer and selecting "copy address as text"