The REV counter on my 03 R50 had a corrupted LCD display - quite a common problem judging by the amount of threads in search results.
However, when doing my research it quickly became apparent that people would often post a question and not get a reply, or receive conflicting answers.
I bought a 2nd hand rev counter from eBay for 25GBP delivered. It was advertised as being compatible with all R50 MINIs from 2001-2006.
The process of swapping the rev counters over is basically plug and play, and shouldnt take you any more than 30 minutes, even if you are a complete novice.
Simply lower the steering wheel in to its lowest position so that you can access the 2x T25 torq screws on the top side of the steering shroud.
Remove the screws, pull away the plastic trim and disconnect the rev counter from the loom. Re-fitting is a simple reversal!
I had zero issues and did NOT need any re-coding doing. Dont believe some of the scare-stories you read on the web. This is a simple and effective fix. Just make sure you buy a rev counter from the same generation MINI and you should be laughing.
I hope this helps someone in the future.....
Replacing the rev counter - some clarification 
