You should get lots of answers to this one, and if you use the search facility you will find it has been covered many times. but to summarise:-
- Don't go to a main VW dealer, they are not specialists and will charge you a fortune.
- A specialist towbar fitter such as https://www.pfjones.co.uk/tow-bars.html is the best route.
- Fixed is cheaper than retractable/detachable.
- ALKO long neck or swan-neck is needed to give sufficient clearance on the ALKO or Winterhoff coupling your van will have.
- get a dedicated plug in wiring harness not a cut and crimp arrangement onto the cars wiring loom.
- 13 pin electrics every time, don't bother with the twin 7 pin of old.
- full functionality allowing fridge operation and battery charging on the run can cost £100 or so more.
- make sure they reprogram the ecu to deactivate the rear parking sensors etc
- cost, you may be lucky and get out at about £500/600, but I would not be surprised if you get quotes of up to £800/£1000.
Colin