Hmm, if you'd asked a few yrs back when I bought a mk4 gti via them, I'd have praised them to the hilt, I got lucky as they found exactly the car I wanted already available at a dealer & I had the car within days, at a nice discount. So I ordered a mk6 thru them & its been farcical (ordered 12th aug & after a load of c&b from the dealer about plenty allocation, nov delivery, now I'm build week 1 ffs). How much of the delay is down to vw is a moot point, but essentially there were other brokers offering much larger discounts, but they were honest & admitted no free slots til dec..........so basically I could have been a lot better off & got the car about the same time. In this I feel the dealer is more at fault than the broker, but they put you in touch, so ultimately it dooes came back to them. I'm very near cancelling & joining the mk5 mob instead 
I did the same and have the same problem as you. I went with another broker (not broadspeed) rather than one i had delt with before (that quoted march delivery and 3% extra discount!) because of allocation now its been put back and back.
After talking to someone i know at a different dealership this is down to VW not the dealers though.
It does seem you either hit luckie at the start of August, or you hit mid to late August were you hit the point VW started dicking about with build slots.
I did have the build slot the dealer said i would have had when i first phoned customer service,
BUT due to VW playing silly buggers with the build weeks this keeps moving to 48 then now 50 and it would not suprise me if it moves again to next year.
I don't blaim the dealer or broker they thought they had the allocation/time scale as VW told them they did! and Customer service said it to me too! Its VW that moved everything about.
