If anyone is doing this addition intending to use the original VW parts to fit a Webasto or Eberspacher I have the hard plastic under shield for the heater spare. It's one that I ordered for this type of fitment but never used it.
Drop me a PM if you are interested.
@Goldie you cannot 'T' into existing fuel pipe (unless you have an auxiliary water heater) as the engine feed is pressurised from the tank primary pump. You need to drop the fuel tank and fit a separate pipe into the tank unit, here in the UK a genuine Eberspacher kit is available for this complete with fitting instructions. I've just fitted mine in a new T6. If you have an auxiliary heater already fitted then you can 'T' into its feed before the metering pump for the auxiliary heater.
I use Bowers at Stoke on Trent as my supplier of Eberspacher parts, they supply a complete kit for a T5/6 currently priced at £635 for a D2 Airtronic with 801 controller or £616 for a Webasto 2000STC with basic rotary controller, other options are available. Eberspacher come with 36 month guarantee whilst Webasto come with a 24 month guarantee. See their website at
http://www.bowerspartsonline.co.uk/
I've no connection with the above company except for being grateful for their excellent service.
Rod