I run Tomtom Navigator 6 on my Orange SPV M600, and with a bluetooh GPS bought off ebay for cheap pounds it does the business of route finding albeit the wee processor in the M600 can lag a bit at times.
I took advantage of a recent offer and got newer maps, but have been fighting with missing POI information that wasn’t appearing on my new maps. It turns out that around about the first download it records which maps to download too then continues doing so. Add a new map and it continues to download to the original. What I had to do is remove the downloaded POIs through Tomtom Home, then add them again. When you try to add them it asks which map to target.