Before I upload, it plays fine on my computer and edits in DirectCut, it's after that nothing will play it.

Do you really mean nothing ? Will WinAmp play them after they have been downloaded ?

I too have DAB (a Psion Wavewinder) and this problem does not happen with any of the software I use. I can upload the MP2 file that comes from WinDAB to my empeg, then download it with emplode and every bit of software I have tried plays it back fine.

Every MP3/MP2 software player I have ever used ignores the file extension and looks in the file itself to work out how to play it, so the fact that the file has an MP3 extension after downloading isn't a problem.

I have compared the file after download with the original, they are exactly the same, every byte.

A side product of this is that the software I'll be using can go straight to MP3, which is something I didn't know until I brought it yesterday evening.

It won't be going straight to MP3 at all. The audio bit stream on UK satellite is MP2, so if your software is outputing MP3 is must be decoding the MP2 and reencoding as MP3, so you will lose quality.

P.S. What DAB receiver do you have, do you have one of the PCI cards ?