Some UK N900s are running a version of the firmware that is NOT available on tablets-dev.. Version 203.2 seems to be a UK thing, but I'm not sure which other regions might use it.. Either way, you can't download it from Nokia so reflashing is changing your device..

https://bugs.maemo.org/show_bug.cgi?id=6878

Feel free to comment in order to try to convince Nokia that they should stop messing the UK about with firmware releases