How about a 5" Navman / Mio?
I've had one of the first TomTom's and they are good bits of kit. The fact though that you have to pay extra for EVERYTHING gets my goat though.
Garmin? I've used a few, and they don't have as good an interface as the TomTom and others IMO - almost too simplistic (which sounds good but can also be frustrating).
Last year I bought a Navman Tourer Europe (Navman as a brand is I think being phased out, but basically they are Mio units rebadged anyhow. These use the same Teleatlas mapping as TomToms, but have good standard features (mine includes free Traffic for life for example).
It doesn't have Bluetooth but it allows route planning on the fly on the unit (adding waypoints) and easily lets you divert off-route to a waypoint such as fuel or food on the fly too and then returns to the original route plan - v handy! It also has 4 route selection options which you can select off the screen if you want to (fastest, economical, shortest and one I can't remember

and you can view them on a map. Its not perfect, but I get on with it well.
I've used mine on the motorcycle (using a weatherproof mount and using the screen not the voice prompts - easy) and in several vehicles and it works well. The voice is a bit tinny compared to a TomTom or Garmin though. I believe these can be had for under £100 now, so thats not too bad either.
Also handy (and a deliberate choice on my part) was that this Sat Nav charges off a mini-usb connection, and at PC USB voltage (5.2v I think). This means that its easy to find a way to charge the thing (e.g. I have a USB charger set-up on my motorcycle so i can run the sat nav, charge my phone or my MP3 player with the same source). 12v Cigar - USB charge converters are common and cheap as well.
As for POI's Speed Camera databases and such (not too much of a worry for me in Sully with a Transit 'Banana 2.5L Diesel non-turbo tbh) then its worth checking out
Pocket GPS World - SatNavs | GPS | Speed Cameras for cheaper and comprehensive Speed Camera POI's for a massive range of PND's (personal navigation device) as well as other stuff for less wonga.
Hope this helps and gives some food for thought. All the best. G.