I tried to use ipodpatcher and it didn't work, it kept saying there was no ipod present. So I looked in the disk management console in XP and noticed it was formatted as NTFS - which didn't sound quite right.
I read that it should be FAT32 and looked for a utility to convert it but couldn't find anything quick so I just downloaded itunes and restored the ipod with that - and now it works.
Its probably a fairly uncommon problem and it wouldn't surprise me if it has been covered somewhere else but I just thought I would mention it as it might save someone a lot of messing about.