Instead of cancelling, why not use this as a bargaining chip to get some money off/extras added for nothing. If it doesn't work then if you can still sack if off should you still feel that way. But if it was me I'd be getting some options added on for nothing!
P1ss poor from VW though, you GTD boys were told June delivery.
Good luck with trying for freebies. Who would fund them, VW or the dealer? Not the dealers fault - look at the info out there, website says they'll be on sale in the UK in June, dealers not told any different. If anything the dealers will be most pissed off by this - for those with p/x, for every month VW are later than anticipated your 2/3 year old Roc/Golf is depreciating, at maybe £250 a month. My Roc value was agreed at £15500, it would probably be on the forecourt right now for £18k. By the time Aug comes around, correct forecourt price will probably be £17k. The dealership expects to make more than 10% on a nearly new used VW.
VW UK are particularly tight with goodwill and useless at resolving customer issues. After my MK5 Golf was clattered by a bus and Benfield took 8 weeks to do a 2 week repair, they left it
1. with the brakes in a dangerous condition.
2. with a paint job so thin and compromised galvanisation so the repair rusted every 3 months
3. with missing items from my boot that were never seen again
4. with the car interior covered in black handprints on the rooflining and metal swarf (from cutting in the new rear quarter) all over the interior.
Some of these issues weren't noticed completely until the following day aas it was pitch black and lashing it down when I picked my car up (I did note the missing items at time of pick-up).
VW UK were involved and I wrote some pretty strong letters of complaint. My goodwill gesture was that VW UK put pressure on to Benfield to offer me a free valet (paid for by Benfield). Apart from remedial paint/rust repairs on the rear quarter panel every 3 months until I got shot of it, I wouldn't let them near the interior again. VW UK said I was stubborn and tried to close my case as "customer satisfied with the outcome". I wrote to VW Germany after that and they were horrified. They gave me 1000 euros compensation for my issues with Benfield and VW UK. You will get short shrift from VW UK for a later than anticipated order.