Best Satnav

Satnavs are normally  a nightmare for us caravan users

But I bought a cmnav adavanced camper from cmnav.co.uk which cost £90

never had a problem with narrow roads here  I am not affiliated with the company just passing info on 

Key Features:

Large 7" screen, for increased visibility, so you don't have to get distracted from driving and take your eyes off the road to stare at the screen.
Capacitive HD Display (doesn't need a stylus, you can use your fingertip to operate it)
256 RAM Memory FAST and NON - FREEZING! 

FREE Sunshade is included, so you don't have to worry about awkward glare or screen reflecting in the windscreen during at night.
You can edit length, width, height of your vehicle so this will give you only the right routes, avoiding low bridges or narrow roads. Also you can specify if you have a trailer attached and number of axles.
Search by UK 7-8 digit Postcode (E.g: WF1 2AB).
Multiple Stop-Offs along the route.
Add your favourite places, missing locations on the map or hazards using "Add to Favourites" feature.
Search by coordinates if your location is not on a public street or doesn't have a postcode.
Speed cameras and traffic lights/red light speed cameras are displayed and up to date.
Driving time management (You can add a second driver as well), manage your driving time, breaks etc.
Narrow roads and Low Bridges avoidance by simply editing vehicle's dimensions using your own, so the sat nav will automatically avoid unsuitable routes for your vehicle. 
TTS (Text To Speech Voices) - Will speak street names, Speed Cameras and other alerts out loud, not only a beep.
Lane selection assistance when leaving Motorways.
Tunnel Animation before entering a tunnel, in order to be prepared for this. 
1000s of Points of Interest such as Camping Sites (UK Camping Sites, Farms, Cottages etc and Rest of Europe - including French Aires), Lay-Bys, Car Parks, Airports, Restaurants and Fast Foods with type of cuisine displayed (e.g - Chinese restaurants will have Chinese flag displayed, Indian restaurants will have Indian flag displayed, British restaurants will have British flag displayed and so on), Supermarkets, Petrol Stations with real logos displayed on screen etc.
Comes with 33 languages and 88 male and female voices from all over the world