Warranty Considerations for fitting a towbar to a 2011 Sharan

I've got a 2011 Sharan and have contacted a few dealersto get a price on fitting a towbar, dedicated electronics and having the ECUrecoded to activate TSP etc. All the dealers appear to contract out the work,which I assume would not affect the warranty. However, if I get an independentfitter to undertake the work, fitting a type approved bar (e.g. Westfalia whichI believe are the ones VW fit anyway) and recode will the car’s warranty beaffected? VW UK cannot did not give me a straight answer.