Changed my colour to Carbon, dealer says it won't alter the build week and also said my BW is showing 27, do I believe that?
I wouldn't believe it. According to my dealer when explaining the cock-up that led to my dad's car changing colour instead of mine, they couldn't change the order a week before "build week confirmed" shows up on the tracker, let alone just before.
What's your tracker status (assuming you have an order number to submit)?
If you're BW27 your tracker status should be updated this week (4 weeks before actual build it should go to "build week confirmed") and at this stage it's likely already scheduled by Wolfsburg. If it''s scheduled then you can't change colour, if it's not scheduled then you can change colour, but that would mean it's at least 4 weeks from being built. If my dealer is correct about locking an order out a week before we see the tracker change then that would imply your car won't be built as early as BW27 if you are still able to change the colour.
Try VW UK for an answer which may be more or less plausible than the one your dealer gave you. Give it a day or 2 after colour change and give them a ring. They should be able to confirm your colour change as gone through and your estimated (if not confirmed) build week.
When I changed my colour, the tracker took 3 weeks to update - not sure how much that was due to the dealer mix-up between mine and my dad's GTD and how much was down to the time it takes for the tracker to update any colour or other option changes.