Looks like the dealer, the leasing company has gone through have had more than there allocation hence the longer lead time. you should be entitled to a hire car for the wait you have had so far. Also the hire car should save you some bik tax (and you could get some money back from your company). That is if you get a car allowance, The hire car from VW should be no cost.
I ordered my GTD on the 31st October and the tracker says it has been built this week and due for delivery end of March. I am more than sure it will be worth the wait given the feedback from the owners lucky enough to have had their's

One of the sales guys at work has just ordered a Golf R today for delivery in May
I was in a similar position to you last year. I had ordered a GTD through work, via a leasing company mid June for a Sept 2013 delivery, which slipped to November then December. I ended up cancelling as they would not offer a hire car from their estimated delivery of end of Sept (they were prepared to offer a hire car from 20 weeks of waiting) then relented to 16 weeks. I got cheeky and asked for keyless as compensation for the extra wait !. Glad I cancelled and have bought as a private purchase.