was ready to sign only to be told there had a problem with the figures quoted previously and it would be x amount more.
Without wishing to sound rude, that's hardly surprising.
As we've discussed previously, you were given "written discounts" etc on figures from campaigns last year that you've been sat on for several months. IMO they were never going to honour those and were just using it as a hook to ensure you didn't walk. They had no obligation to honour those discounts and with new campaign rates starting a few days ago it doesn't surprise me to see the discounts get pulled. Christmas/Jan is the quietest time of the year for the car trade, so incentives are at their highest, those incentives get small er and smaller the further we get towards spring. At the end of Jan discounts had gone from 15%+ to below 10%, and even though VW are chucking in another £500 to the deposit contribution, it's still a lot less than it was.
There is still a small chance they are playing a game, and they may buckle by you walking away, but if they're confident on their targets and/or the deal previously offered simply isn't possible given the new margins set by VW, then you might be onto a losing battle. My advice(FWIW), if you are intent on getting a car act now, because as we go further towards the spring/summer discounts will only continue to get smaller and you will be forced into the used market. Do this by either accepting the price, or trimming back on options. By the sounds of it though it might be too late to get the spec you want?
Good luck though, I hope you can get the car you want.