It depends if you want to work with your dealer, or against them. I choose the latter option, but here I am, eight (almost) months later still having problems. However, I can say that my dealer have remained supportive of me and have never questioned any of my quality-related issues. They have never tried to "get out" of repairing a fault and, of those, there have been so many.
I'm not going to send this thread off in the direction of moaning about the quality of the new car, as I'm sure it's been done to death - here and elsewhere.
I'm actually suprised that you're having problems as the quality issues had gone quiet for a few months and people we begining to settle into getting on and enjoying (read: moding, for some

) their new cars. I had been assuming that VW were getting on top of them.
Anyway, two very big factors in your ability to reject the car:
1. Is it on finance (if so it's not yours to reject and you can't). But your finance company can. You need to involve them in all correspondence. In this case, you are acting under the Supply of Goods Act (1973 I think), not the Sale of Goods Act (1979), as amended.
2. Have the dealer attempted to repair faults. If so, your ability to reject the car outright has probably been lost. You will now be in the domain or trying to get the car to qhat it should be.,
Also, you only have a "reasonable time" in which to reject the car. Although there's no legal definition of what this is, it is what a "reasonable man" would consider to be "reasonable" - in other words 28 days.
Three things a product must be when sold:
1 - "As described" - not a problem
2 - "Fit for purpose" - well, you can drive it and use it as a car, I guess, so doesn't apply to you
3 - "Of satifisactory quality" - this is likely the slant to go in on - VW being a semi-aspiration brand, and all.
What are the nature of the other three problems?
If it's just the fuel cap solienod that's gone, that I would take it on the chin and get the dealer to repair it.
I'm lucky through, my dealer is just 2.5 miles from my house, so it's relatively easy for my to put the car in for these sorts of minor repairs.
Oddly, lately, I'm putting the weight back on, which must mean that 2.5 mile walks to/from the dealerare getting less frequent!!
Anyway, if you're really unhappy, go to your CAB. They'll likely just refer you to your local Trading Standards office (that's all mine did, anyway). Lodge a complaint against the dealer at Trading Standards if you feel that strongly against it. I simply spoke to them, they gave me lots of really good legal advice (esp. the stuff about supply of goods vs. sale of goods). I didn't formally report the dealer to them.
I did fight VW UK for compensation and got some!! But any issue of rejection is btwn you and your dealer (this is why is might not be the best idea to fall out with them) because that is where the contract exists.
Deek.