So if you go the broker route, then its advisable to sell your car privately? I've just done a Broadspeed quote and they're £2,341 cheaper than VW - that is a massive saving. Has anyone actually used Broadspeed before? Am wary of a "too good to be true" scenario 
Brokers are fine as long as they are the middleman for a UK VW dealership and not bringing in grey imports (you don't hear about grey imports from Malta/Ireland much now, but they are usually missing UK specced equipment - maybe smaller wheels, no fogs etc). You will get the best price for your trade-in privately. The dealerships don't give you a great price through a broker AND a great part ex price. Sometimes they're robbing peter to pay paul in that respect.
If you're trading in a nearly new Golf though, many people prefer dealing with a dealership for a used £12k Golf than buying privately, so it can be hard to go the private route. Don't forget the commission fee you have to pay to broadspeed when weighing up your "deal".
For my circumstances it looks like they value my current car at £14200 and would save you £2300 on list for my GTD. The part ex I got is £15500, £1300 more than the broadspeed part ex value. Broadspeed want £200 fee, so at the moment I am £800 better off with broadspeed than through my dealership deal. Factor in the GAP insurance they gave me and the servicing package and we're talking negligible gains and the inconvenience of maybe going halfway across the country to pick up the new car depending upon where their prefered dealership is.
For me in my current situation it's not worth the bother, but I tend to use the brokers prices and low part-ex as a yardstick to determine the "cost to change". Ask for £2300 off the list from a main dealer for a GTD right now and they'll tell you to get lost. Ask for £1000 off when they're valuing the part ex at £1300 more than the broker and you might get a deal. The cost to change will be the same going via either route.
If you have no part-ex to chop in then by all means go the broker route - easy discount! Brokers can leave you waiting longer for your car if the supplying dealership gives preference to it's normal retail customers for it's limited allocation on the limited supply stuff though.
