Hi Houchen
If you have identified the company to do the retro fit, they will be able to advise accordingly.
There are two companies I am aware of that could do this for you.
HazzyDayz Days In Markyate (near St.Albans) & Sat Nav Systems (Chertsey), There May be others, you should ensue OEM parts and that the company fitting them are VW approved, to prevent potential warranty issues.
Below is a link from both companies website for a retro fit cruise (stalk type).
If you have the MFSW with the cruise option deleted, it should be possible to add the required button(s) as in the original spec.
I know that Fitting Acc is not an option due to insurance implications for the company, confirmed by Sat Nav systems via email.
Cruise control makes long journeys on motorways safer and more comfortable by regulating your car’s speed. The Volkswagen cruise control system works electronically to help regulate your car’s speed. It can reduce the stress and offers some comfort on long journeys by maintaining a constant...
www.satnavsystems.com
This is for the supply and fit of cruise control to your VW Transporter T6. This is the stalk variant, we can also offer the Multifunction Steering
www.hazzydayz.com
I hope this helps.
I have personally used Sat Nav Systems for retro fit of a factory tow bar and replacement head unit (missing DAB function from factory) I can highly recommend them.
Hazzy days comes highly recommend also.
Both offer a home fitting service for a fee